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7 hours, 57 minutes

A Wall Street Journal bestselling series. A deep diving investigator is pulled into the depths of a string of unsolved serial murders in a riveting thriller by the Amazon Charts bestselling author of Sea Storm.

When a young woman washes ashore on a Fort Lauderdale beach, Sloan McPherson of the Underwater Investigation Unit is called in to consult. Sloan’s instinct says murder, but even then, there are too many questions.

For answers she reaches out to Gwen Wylder. The Miami homicide detective is notorious for being manipulative, bitter, a tyrant to her peers, and wicked smart. And she demands something in return from Sloan: fresh insight into seemingly unrelated cold-case murders and disappearances—and a possible serial killer trolling the Florida coast.

As loose ends of the old files begin to come together, another woman disappears. Sloan and Gwen are certain she’s the newest link in a deadly chain. They are determined to track her down before she dies, but they soon find themselves in uncharted waters. And the deeper Sloan and Gwen go, the stranger the case gets.

312 pages, Kindle Edition

First published February 21, 2023

1795 people are currently reading
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Andrew Mayne

69 books2,931 followers

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Displaying 1 - 30 of 496 reviews
Profile Image for carol. .
1,755 reviews9,987 followers
December 9, 2022
Not enough cowbell underwater.

For every thriller/mystery series, there is a style and a place, and that’s part of the attraction. Conversations go like this with my mom: “Do you want me to order a Nevada Barr book?” Is that the one with the female ranger who works in different national parks?” “What about Elvis Cole and Joe Pike?” “Those are the ex-military guys who live in Los Angeles?” “Do you want a Walt Longmire?” “Is that the Wyoming sheriff?” In Andrew Mayne’s series, the hook is that the lead, Sloan McPherson, is a talented diver and one of the select few of Florida’s unique Underwater Investigation Unit.

Unfortunately, Sea Castle is landlubber-focused, with the exception of the opening scene and a small detour mid-book. I’m sure authors get bored and think changing up location and focus will keep the magic alive, but fourth book in a series seems too early–we’re still finding our zone. Ben Aaronovitch did it with Foxglove Summer, one of my least favorite of his series, and Mayne does it here, with equally dubious results for me.

The elements that played together in the first three books–the camaraderie, the water-based, risk-taking teamwork, the dive scenes–are largely absent here. The Underwater Investigation Unit remains in limbo, victim of political forces from book 3, resulting in Sloan’s temporary reassignment to a manager that doesn’t want any heat. When a body discovered at the beach, Sloan chases a lead to the maverick detective Gwen Wylder. From there, an uneasy partnership develops. The multiple cases take Sloan out of her element–literally and figuratively. Another hallmark of the prior books has been the challenge of how Sloan balances personal and professional life, with a number of home scenes to build the feeling that it is a genuine concern for her. In this book, there’s some family contact by phone, but it is minimal–this is definitely a reverse-episode of all the interactions we had come to expect.

The writing is usually solid, although there are some instances where it could use polishing. In the previous two books, I thought Mayne’s writing above average for genre, so I feel like it must be because I read a very early advance copy. I’ll note that the awkwardness wasn’t bad enough to prevent the story from capturing my attention. I’d love to have a dialogue with other readers on whether or not Mayne achieves a gender-neutral or female-experience voice. Every now and then there was a phrase that just cracked me up with Sloan’s unique thinking:

“I’ve learned that you never win a battle of wills with a crazy person because they don’t even know there’s a battle. The best course of action, whether it’s a bull shark that’s decided to follow you or someone like Gwen, is to keep moving and not give them a reason to snap.”

The plot was unusual, and one thing you have to give Mayne credit for, he’s not going for body-of-the-week scenario. You can usually count on some slight of hand or an interesting plot twist in his stories, and this did not disappoint. Sloan, however, is a little slow on the uptake. For a woman who was raised by a family of ‘pirates,’ she sure is gullible. Spoiler-ish, the motivation for the villain is one of my least favorites in the thriller world. Did I believe it? Maybe? I found it highly unlikely for a couple of reasons, which I will definitely bury under spoilers.

More concretely, the plot wrapped up abruptly with a couple of pages and a non-sequitur afterward. Literally, I re-read the ending because I was not sure what happened to one of the major characters. I’ll note that I did read a very advance reader copy, an uncorrected proof, which meant there were a lot of awkward formatting issues that sometimes made it a little hard to follow. Funny; I had no idea that that would throw my reading rhythm off so badly. I suppose it’s like finding verse in the middle of the prose, and to be honest, I hate it when fantasy authors do that. You know those songs some of them liked to include, like you were hearing them sing around the campfire? Yeah, I never read them. I’m not blaming the author as much as offering a possible explanation for why it felt choppy at times–because the formatting was, you know, literally choppy. So I might have missed some bits.

At any rate, an enjoyable book that I think people who are looking for a mystery/thriller will enjoy. Based on the great experiences I had with Black Coral and Sea Storm, it didn’t really meet my elevated expectations–or rather, explore those bottom depths of the ocean or Florida swamplands. I guess that’s the challenge of being a high achiever.

Many thanks to NetGalley for the advance reader copy
Profile Image for PamG.
1,294 reviews1,031 followers
February 22, 2023
Andrew Mayne brings action, suspense, and mystery to Sea Castle , the fourth novel in the Underwater Investigation Unit series. Sloan McPherson, temporarily reassigned to the Florida Department of Law Enforcement from the Underwater Investigation Unit (UIU), is called in to consult when a young woman washes ashore on a Fort Lauderdale, Florida beach. Sloan believes the woman has been murdered, but others aren’t so sure.

For answers, Sloan reaches out to Miami homicide detective Gwen Wylder. Gwen demands fresh insight into some cold-case murders and disappearances in exchange for her help. As the old cases are worked, another woman disappears. Sloan and Gwen are sure she’s the latest in a deadly chain. However, this case isn’t straightforward.

This novel is very different from previous novels in the series with Sloan and her old partner Scott Hughes from the UIU being reassigned. Sloan takes center stage in this one with cameo appearances by Scott Hughes and their previous boss, George Solar. However, it still has amazing characterization and a solid mystery to solve.

Sloan has good reflexes and amazing instincts. She also has a discerning sense of justice and determination that makes it easy for readers to get behind. However, she takes risks and has trouble with people who ignore clues and go for the quick resolution. Gwen is manipulative, argumentative, abrasive, and rude. She’s also extremely smart, a great detective, and she’s always the victim’s ally.

The plot is complex and has twists and turns to keep a reader guessing. It easily transports readers into the terrifying world of the victims and the investigators. The high stakes kept me engaged throughout the story. The well-written story and the incredible characters combine with action and multiple mysteries to culminate in an amazing conclusion. Mayne is an exceptional storyteller who provides readers with gripping scenes that move at a blistering pace. The final chapter provides the thread for the next book in the series. My main quibble with this book was I missed the diving and underwater aspects that have made this series unique among law enforcement and police procedurals. Themes include deaths, disappearances, political pressure, family, friendship, and much more.

Overall, this was an intense story with complex characters that kept me turning the pages. I was surprised several times by events. This kept the tension level high throughout the book. There was enough background in the novel that it worked well as a standalone, but I am looking forward to reading the first two books as I wait on the next one in the series. Those who enjoy crime thrillers, mysteries, and police procedurals may want to check out this novel.

Thomas & Mercer and Andrew Mayne provided a digital ARC of this novel via NetGalley. This is my honest review. All thoughts and opinions expressed in this review are my own. Publication date is currently expected to be February 21, 2023. This review was originally posted at Mystery and Suspense Magazine.
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My 4.09 rounded to 4 stars review is coming soon.
Profile Image for Linda.
1,652 reviews1,703 followers
January 26, 2023
It's only cold if you're standing still.

Special Agent Sloan McPherson knows cold cases. She's part of the Underwater Investigation Unit of the Florida Department of Law Enforcement. Her team has been set on the sidelines for a while. Sloan has been relegated to leaving footprints on land for the time being.

Let's introduce you to Sloan. Sloan's father is a treasure hunter in Florida and is more fish than mammal. She has a thirteen year old daughter, Jackie, with her partner, Run. While her father is more fish, Sloan is more bloodhound as she's cracked open some of the most difficult cases on record. She's a dynamo, but she's also painfully human and she's well aware of it.

Latest case: A body of a young woman has been found dead in the waters near the coast. The woman had a rope tied around her neck. Nicole Donnelly was from Atlanta. Tourist or here for other reasons?

Now here's where Andrew Mayne flips the script. It's been suggested that Sloan work with Miami Homicide Detective Gwen Wylder. Wylder has quite the reputation on the force. And that reputation has her missing a few nuts and bolts in the upper shelves of her mind. Wylder is tredding water in the department's basement awaiting retirement. But Wylder is not going out without making inroads into stacks of cold case folders on her desk. A partnership in Heaven or more likely Hell?

Andrew Mayne has created two cast iron women forged in different manners. We'll experience Sloan's outright honesty in dealing with Wylder and Wylder's cantankerous, cutthroat attitude with Sloan. Mayne knows how to insert snappy and snarky dialogue in just the right spots with humor sometimes leading the way.

Sea Castle is one tightly wound psychological thriller with all the bells and whistles. Andrew Mayne is known for his expertise in carving out characters with a well-honed hammer and chisel. And it all works like a fine-tuned machine. Sea Castle can be read as a standalone. We've got another winner in the talented hands of Andrew Mayne.

I received a copy of this book through NetGalley for an honest review. My thanks to Thomas & Mercer and to the talented Andrew Mayne for the opportunity.
Profile Image for Liz.
2,825 reviews3,732 followers
February 26, 2023
Sea Castle is the fourth in the Underwater Investigations series. This time, the UIU department has been temporarily disbanded. Sloan is sort of at loose ends before being paired with Gwen Wylder, a Miami homicide detective with a well earned reputation for being bitter, and maybe even a bit nuts. The two are investigating a current murder that maybe tied to others, suggesting a serial killer.
Gwen was an interesting character. Single minded, prickly and like a dog with a bone, hard to shake once she gets an idea. I missed Sloan’s old team. The plot here is slower and lacks the constant action of the prior three. It’s much more of a psychological thriller. It also takes place on land with only minimal time spent even near the water.
This time the real star of the book is the villain, who is a master manipulator.
The one fault I have with this series is that Sloan seems able to be the superwoman of sleuthing, finding obscure facts no one else can. It strains believability, but it didn’t affect my enjoyment.
My thanks to Netgalley and Thomas & Mercer for an advance copy of this book.
Profile Image for LIsa Noell "Rocking the chutzpah!".
736 reviews578 followers
October 3, 2022
My thanks to Thomas and Mercer, Andrew Mayne and Netgalley. I love Sloan. I also love the UIU. The main reason I read these books are for both! This book had no UIU. Sloan comes in and unbelievably solved 2 cases "one a serial" in less than 48 hours. Something that had been in the books for quite a few years. So..that's completely ridiculous. Yet? It's Andrew Mayne! I expect that. I hated that this was mostly on land. Still, I quite enjoyed the crap out of it!
Profile Image for Matt.
4,822 reviews13.1k followers
January 13, 2023
First and foremost, a large thank you to NetGalley, Andrew Mayne, and Thomas & Mercer for providing me with a copy of this publication, which allows me to provide you with an unbiased review.

Andrew Mayne returns with his somewhat unique series, set in the heart of Florida. Using a forensic diver as his protagonist, Mayne is able to tackle a different angle to most crime thrillers I have read, while keeping the reader intrigued until the final page turn. Adding some serial murder and cult-like behaviour, Mayne shows that he has all the ingredients for a great novel, sure to keep the reader enthused.

Sloan McPherson has made quite a name for herself in Fort Lauderdale as a member of the Underwater Investigation Unit’s forensic diver. When the body of a young woman’s body is found along the shoreline, Sloan immediately presumes it’s murder, while others ponder the possibility that she might have committed suicide. The clues do not make sense and Sloan is baffled as to what she is seeing in front of her.

Sloan begins poking around, but she is stonewalled by the authorities, as they are sure this was a simple miscalculation by a novice swimmer. Enter Gwen Wylder, who is quite rough around the edges and an outcast with the Miami Police. Wylder is happy to help Sloan, but for a price. Sloan must help by offering her own insight into some cold-cases that Wylder has been amassing, all part of what could be a serial killer who has been conniving while they traipse across Florida without detection.

As Sloan soon sees, her victim fits perfectly into the larger case study and there is proof that a killer could be travelling across the state, killing young women. Another woman goes missing, leaving Sloan and Wylder to race out so they can stop a killer from striking again. As things get more intense, both women find themselves involved in something they could not have expected, where they are not able to extricate themselves with ease. Mayne creates an intense story and keeps the reader hooked with some of his unique perspectives throughout.

It was the first book in this series that alerted me to the work of Andrew Mayne. Since then, I have not been able to get enough, having devoured a few of his series, while always remaining in awe. Mayne knows what he’s doing and keeps things fresh, unique, and on point. Whenever I see a new publication of his, I cannot help but rush to get it, knowing that it will be a stellar piece of writing.

Mayne develops his narrative in such a way that the reader wants to learn more. He knows how to present a tale that balances the criminal element with some strong backstory, all of which is essential to the final product. Great characters, some of whom build their development throughout the novel, provide the reader with some entertainment as they continue with the journey. The forensic perspective, mixed with the plot development, offer something unique, though this book steered away from underwater exploration and more to the chase for a killer. While this is not as enticing as some of the earlier novels, Mayne is still able to keep the reader in the know and dazzle with his writing style!

Kudos, Mr. Mayne, for another great piece of writing!

Love/hate the review? An ever-growing collection of others appears at:
http://pecheyponderings.wordpress.com/
Profile Image for Carol.
3,761 reviews137 followers
May 21, 2023
A corpse washing ashore proves to be just the beginning. The discovery of a dead girl with a rope around her neck on a Fort Lauderdale, Florida beach triggers a call to detective Sloan McPherson of the Underwater Investigation Unit. Medical examiner concludes that Nicole Donnelly was strangled, but by hand, not by a rope. This is the first of several inconsistencies that make Sloan suspect that the case will be complex, a hunch that’s confirmed with every new twist in her investigation. Mayne’s fourth thriller reads like a long-running, forensic crime TV series, with a huge cast of smart witnesses and lots of regulars who make short appearances over several chapters. Although Scott Hughes, Sloan’s partner in previous installments, is away in training, she finds welcome support from veteran detective Gwen Wylder, the perfect partner for a case focused on women at risk. Clues emerge at a truck station that may be the scene of more unsavory sexual activity; in the ocean, courtesy of an Underwater Robotic Vehicle; and through a trio of less than desirables that Sloan identifies by the names he's associated with them, "Silver Teeth", "Brio", and "Half Face"...and a charismatic cult leader. The plot comes together like the proverbial jig-saw puzzle, each piece added a little more to the very disturbing big picture that was forming. I enjoyed the mystery and the characters but wished there had been a bit more taking place in the water, but Andrew Mayne as written an excellent mystery.
Profile Image for Sophie.
223 reviews209 followers
November 16, 2022
Just finished Sea Castle by Andrew Mayne and let me tell you, it was a wild ride! What an amazing thriller! I won't lie, Andrew Mayne could write a book the history of rocks and he'd make it interesting.

When an unexpected young woman washes ashore, Sloan McPherson is called in to consult. Teaming up with Gwen Wylder, Miami homicide detective, Sloan sets out to solve mysterious cold-case murders and find a possible serial killer. Gwen Wylder has a notorious reputation for being manipulative and wicked smart - but can she help crack the case?

Sea Castle by Andrew Mayne is a page-turning thriller that kept me on the edge of my seat the whole way through. When a young woman washes up on the beach, Sloan McPherson is called in to investigate and soon realizes that this isn't just any ordinary case - it's something much more sinister.

The characters are well developed and easy to sympathize with, and the plot is fast paced and exciting. With twists and turns aplenty, the best way to describe my experience with Sea Castle is a roller coaster ride through time and intrigue 🎢

I received an advanced reading copy of this novel from the publisher through NetGalley. I write this review voluntarily.
Profile Image for LIsa Noell "Rocking the chutzpah!".
736 reviews578 followers
October 2, 2022
My thanks to Thomas and Mercer, Andrew Mayne and Netgalley.
I love Sloan. I also love the UIU. The main reason I read these books are for both!
This book had no UIU.
Sloan comes in and unbelievably solved 2 cases "one a serial" in less than 48 hours. Something that had been in the books for quite a few years.
So..that's completely ridiculous.
Yet? It's Andrew Mayne! I expect that.
I hated that this was mostly on land. Still, I quite enjoyed the crap out of it!
Profile Image for Jim.
581 reviews118 followers
April 16, 2023
The Underwater Investigation Unit (UIU) has been disbanded following the events of Sea Storm and Sloan McPherson has been reassigned to the Florida Department of Law Enforcement (FDLE). She is still the go to person in cases involving water though. When the body of Nicole Donnelly is found on the shore of a Fort Lauderdale beach with a rope around her neck Sloan gets the call.

Was it an accident? Suicide? For her there are many questions but she is afraid her colleagues are ready to write this off and close the book. They have mentioned a Miami Homicide Detecive named Gwen Wylder and Sloan reaches out to her. Turns out that Gwen has quite the reputation. She is bitter, a tyrant, and manipulative. She has been relegated to the basement.

Before she agrees to help she asks Sloan to look as several other cold cases. Feeling she has no other choice if she wants Gwen's help Sloan agrees. Manipulative. When another woman disappears Sloane and Gwen work together to try and find her before she too dies.

Sloan and Gwen are totally different characters. Both have reputations. They don't necessarily fit in the system. For different reasons. Gwen is looking to close cold cases before she retires. Sloan is looking for justice for the victims and often puts herself in harms way. In the past her partner, Scott Hughes, has been there to save her but he is off somewhere else. Fortunately it appears that maybe Sloan has learned to look before she leaps. It was interesting to see the relationship develop between Sloan and Gwen. Gwen comes with a lot of baggage. Can Sloan and Gwen work together and save the missing girl before she becomes the latest victim?

Will the UIU be back? Will George Solar and Scott Hughes return?
Profile Image for Mogsy.
2,265 reviews2,777 followers
February 24, 2023
5 of 5 stars at The BiblioSanctum https://bibliosanctum.com/2023/02/23/...

Sea Castle is probably the best book and my favorite in the Underwater Investigation Unit series so far, but ironically, it also features the least amount of underwater investigation. That’s right, UIU is taking a break, at least the time being. When the book starts, the unit has disbanded, and Sloan McPherson has been reshuffled to another part of the Florida Department of Law Enforcement when the body of a young woman washes up on shore, and our protagonist is called up to the scene for a consult.

And that’s pretty much all the wetsuit action you’ll see in Sea Castle.

Still, while her new colleagues are ready to rule the case an accident or suicide, Sloan isn’t so sure. There are certain elements that don’t add up, making her suspect that the victim was murdered.

Unfortunately, the only other person who can help her find the killer is Gwen Wylder, a curmudgeonly old detective with a reputation for being difficult to work with, and sure enough, Gwen makes Sloan jump through all sorts of hoops before she would agree to hear her out. Happily, our girl aces all the tests, even making headway on a couple of Gwen’s cold cases, impressing the older woman and setting the two of them on the trail of a crafty serial killer who may have hunted the Florida coast for years without detection.

Author Andrew Mayne is back on form with this fourth installment in a series that I’d been concerned was starting to fizzle out. Truth be told, I wasn’t crazy about the last book, Sea Storm, which I felt was weak on plot and lacked the typical levels of excitement I’d come to expect from the author’s work. To be fair though, Sea Storm also relied heavily into the internal politics of law enforcement and government for its intrigue, and to each their own, but I just wasn’t a fan. I’d much rather my mystery thrillers be about solving cold cases and chasing serial killers, thanks.

And that’s what Sea Castle was all about! I loved everything in this book from its twisted, unpredictable plotline to its dastardly mastermind villain. It didn’t even matter to me that we got hardly any underwater action, though I can see how the lack of it might jar some readers considering it’s the main hook of the series. Characters we’d gotten to know from the first three books, like Scott Hughes or George Solar, were also largely absent, which might be another point against Sea Castle.

For me though, all that was definitely a plus. Taking Sloan away from her comfort zone and the people she worked with gave new life to this series, and allowed someone like Gwen Wylder to come into the picture. Despite her cantankerous ways, I really liked Gwen’s character and her relationship dynamic with Sloan. While their personalities can’t be any more different, the two worked well together, no doubt because they’re both incredibly intelligent and driven. Even if their partnership ends up being a one-off for this book, I really hope this won’t be the last we see of Detective Wylder.

Lastly, everything that makes Sea Castle such an atypical UIU book also means that it can work great as a standalone. If you’re curious about the series and find catching up with the first three books daunting, you may find this one very accommodating to newcomers as a place to jump on board. Speaking as a big fan of Andrew Mayne who reads all his books, I also think this is one of his best in years.

Audiobook Comments: Hats off to Susannah Jones for another wonderful performance as narrator, giving the perfect voice to a strong female lead like Sloan McPherson. I love her work and she never disappoints.
Profile Image for Valleri.
1,009 reviews43 followers
October 14, 2022
BIG thanks to both Thomas & Mercer and NetGalley for the opportunity to read and review an early copy of Sea Castle!

Sloan McPherson of the Underwater Investigation Unit is called in to consult when a young woman washes ashore on a Fort Lauderdale beach. The detectives say suicide but Sloan says murder. For assistance, she turns to Miami homicide detective, Gwen Wylder, who is known to be a manipulative, bitter tyrant. From there it's hang onto your seat time!

Is this book completely realistic? Not on your life! Are there too many times it seems as though ESP is being used by Sloan? Not on your life!😉 For some reason, those things didn't bother me at all. I absolutely loved Sea Castle!! The twists kept me enthralled.

I highly recommend this series, which has previously been about deep-sea diving investigations. I wasn't sure I was going to like Sloan working on land but it was a fun read!!
Profile Image for Natalie Mackay.
249 reviews1 follower
May 8, 2025
Saw the twist coming but it was still brilliant.
Profile Image for Suzi (Lil Bit Reads).
891 reviews61 followers
February 20, 2023
Sloan McPherson of the recently-dispersed Underwater Investigation Unit (UIU) is called in to investigate when the body of a young woman washes ashore in Fort Lauderdale. Local law enforcement seems eager to wrap up the case quickly, but Sloan is convinced that the young woman was the victim of foul play. Sloan soon finds herself teamed up with a bitter old Miami detective to solve the case as well as some old cold cases.

Although this is the fourth installment in the UIU series, it can easily be read as a stand-alone novel. Although Sloan’s old colleagues from the UIU are mostly absent here, she has met her match in Detective Gwen Wylder when it comes to circumventing authority and determination to solve crimes regardless of the danger or consequence. Sloan is a fantastic character, a strong female protagonist with a rebellious streak and a passion for bringing baddies to justice.

Sea Castle isn’t as action-packed as the previous installments in the series, but the plot was twisty and thrilling enough to hold my attention. Because the UIU has been sidelined, Sloan’s in/on water activities are mostly tangential to the storyline. I’m eagerly anticipating the UIU being reunited for more underwater adventures in the next installment!

Many thanks to NetGalley and Thomas & Mercer for providing me an advance copy of this book.
Profile Image for The Humble Jess.
388 reviews29 followers
February 28, 2023
The book was deceiving. It's called Underwater Investigation but yet...there was very little of underwater investigating which is part of the whole series....

I think Andrew Mayne is a good author BUT he went off track with this book. I read to page 125 then I skipped to the very last chapter. I had NO desire to actually read the damn thing. There was so little underwater anything, I really have NO CLUE why Andrew Mayne made a book four. It really makes no sense. If I remember correctly, the underwater unit was disbanded in book three in which case THIS BOOK should have never been written considering 🤦🏽‍♀️. If your going to disbanded the underwater unit in book three then it should be a 3 book series not a four. Four makes no sense. Maybe I'm just smart that way 🧐🤔.

I read the last sentence in the book where supposedly the unit comes back in the next book but even so..how many readers are going to be reading THAT? As an author you want to engage your readers not lose them LOL and he did just that with this book. This had very little of underwater soooooooo yea. I'm not sure how we're supposed to engage with book five lol after a book hiatus which is pretty much was. Mayne put his readers on hiatus with this book that made no sense and I don't like it. But that's just me.

Profile Image for Julie.
1,653 reviews72 followers
October 31, 2022
Thank you NetGalley and Thomas & Mercer for the copy of Sea Castle. I love Andrew Mayne books because his characters always leap off the page and I live with them while I am reading. Sloan is a great character as always. The wild card is Gwen, who I don’t think I would like in real life, but as a character was amazing with her single mindedness and drive to prove herself. Little touches, like the Lao’s coffee incident, seem insignificant but serve to humanize the characters and make them more real. If you love a twisty story, you will love this book. It was hard to know who or what to trust. This is the fourth book in a series, and it can be read as a stand alone, but do yourself a favor and read the series because it just keeps getting better and better.
Profile Image for Yvonne (It's All About Books).
2,693 reviews316 followers
February 4, 2023

Finished reading: February 4th 2023


"I've learned that you never win a battle of wills with a crazy person because they don't even know there's a battle."

*** A copy of this book was kindly provided to me by Netgalley and Thomas & Mercer in exchange for an honest review. Thank you! ***



P.S. Find more of my reviews here.
Profile Image for Ray Palen.
2,006 reviews55 followers
March 25, 2023
Author Andrew Mayne has worked as a magician/illusionist and even had a cable series entitled Don’t Trust Andrew Mayne. If readers of his clever novels take that recommendation to heart it will make for less sleepless nights of reading as his stories have become famous for their literary sleight of hand.

SEA CASTLE is the latest novel in the terrific and very unique Sloan McPherson series. Note, I did not refer to this as an Underwater Investigation Unit novel because that team was disbanded after they ruffled some very powerful and influential state government feathers in the prior novel, SEA STORM. Sloan has now been redistributed within the Florida P.D. system and finds herself literally tripping over her next assignment when she discovers the nude body of a female on the beach in Fort Lauderdale.

Sloan’s initial thought is that this woman must have been murdered somewhere else and left there. This suspicion is confirmed when the Medical Examiner determines that the body was in the water approximately 20 hours after death. Sloan does her own experiment to re-confirm her feelings by placing the body of a large pig in the same body of water to see how long it took for a local shark to take a nibble. The nibbles begin mere minutes after the pig was submerged, proving that the pristine body of the deceased young woman could not have lasted 20 hours in that same waterway.

The Fort Lauderdale Police do not have the time or manpower to devote to this case, but Sloan is insistent that she wants to run with it. The only way that her new boss can shut Sloan up and get her out of her hair is to push her towards the area pariah in the department. Former Miami Homicide Investigator Gwen Wylder has been shut away in a basement office away from active cases because of run-ins with her colleagues and accusations of being difficult to work worth and having lost the trust of the rest of the department.

After a rocky start, Sloan finds herself connecting with Gwen as they are indeed two of a kind and surprisingly similar in their status with the law enforcement community. Gwen listens to Sloan’s description of the body found in Fort Lauderdale, whose cause of death was put down to strangling, and sees an opportunity to tie this case to several cold cases she has never been able to solve over her years on the force. The fact that the deceased was identified as a woman from Atlanta makes things even more suspicious. What brought her all the way to Fort Lauderdale to die?

Suddenly, the loose ends of Gwen’s cold cases and various female disappearances begin to tie together. They are able to identify a woman named Carla who they deem to be the next victim of the alleged killer. It appears that the killer has been acting as a sort of guru, using different names each time, to lure young women into what feels like an occult or coven situation whereby they are sexually assaulted and then killed. Sloan and Gwen take Carla with them wherever they go as they attempt to glean as much information as they can from her.

A high-speed chase with the alleged killer ends with the killer’s car smashing into a tree and him getting away. However, Sloan and Gwen find the body of another intended victim, still alive, in the trunk of the crashed vehicle. This young woman named Riley should be the ideal next witness in their case against the killer. The only problem is that Sloan feels something is not adding up with the case and needs to figure out what might be causing her self-doubt before the killer strikes again.

SEA CASTLE is an above-average thriller that never ceases to surprise the reader. I recently watched the Hulu movie The Boston Strangler which alleged that the convicted killer, Albert DiSalvo, may not have acted alone. Like Sloan McPherson, readers of SEA CASTLE will get that same feeling while reading this novel and that makes the experience Andrew Mayne has created for us one to truly savor!

Reviewed by Ray Palen for Book Reporter
Profile Image for Erin Sullivan.
300 reviews7 followers
July 22, 2023
So many twists and turns! I didn't know who to believe and who was guilty until the end!

It was described to me as a thriller, but I would say it's more of a mystery/detective story. It wasn't super thrilling, no jump scares or even any creepy stuff.
Profile Image for ❀ Crystal ✿ -  PEACE ☮ LOVE ♥ BOOKS .
2,532 reviews308 followers
February 28, 2023
ARC provided by NetGalley for an Honest Review
Sea Castle was another action packed sea-venture in the series. From start to finish the book was interesting and engaging. I was immediately sucked back into this world even though it’s been awhile since I’ve read the last one. While the book could be read as a standalone it’s highly recommended you read the series in order for both continuity and an understanding of the heroines history & background. By the end this was a pretty insane read once the twisted killer was revealed. So scary that someone so evil could be able to manipulate technology like an expert level hacker. While I was mildly shocked about the villain this book read more like Criminal Minds episode towards the end than the CSI Miami vibes I’ve gotten in previous books. I’m a fan of both so zero complaints from me as I kinda liked the more psychological aspect of this book. A killer that preys on vulnerable women like a twisted cultist is honestly terrifying to me. The way people such as sociopaths are able to manipulate and control other human beings, heck their very lives, is something most of us could never grasp. And now with technology it’s even easier for people to connect and even spy or stalk victims if your skilled enough. Sloan seemed even more badass in this book and as always I truly love her backbone. Also seems she’s finally gaining the reputation she deserves among her peers. I mean she’s a badass cop and something fierce/fearless in water. She’s the total package for law enforcement in the Miami are 😛 I listened to the audio of this book and have nothing bad to say. The narrator definitely helped build up the tense moments and made for a wonderful and intense read!
695 reviews14 followers
October 27, 2022
Having read many of this author’s books I was beyond excited to get an early copy of the fourth in a favorite series, Underwater Investigation. It’s such a unique niche in the crime, murder mystery genre. It could be read as a standalone, but getting to know previous cases of the primary character, Sloane McPherson, will give perspective to where she is now.
Sloane has family history in South Florida where she’s called to the scene of a woman’s body on the beach. The underwater investigation team is in disarray as George Solar tries to justify it’s existence and value. As an experienced diver Sloane is often working with various agencies. Her career path takes a sharp right turn when working a new case leads to a deep dive into several cold cases. She’s trying to balance work and be present as a Mom while insulating her teenage daughter, Jackie, from dark violent crimes.
Sloane is paired with a former detective, Gwen, who’s obsessed behavior landed her in a basement full of cold cases. She’s a sharp, bitter, angry, intuitive crazy woman. Gwen is disregarded, made fun of and shunned by her peers. Her abrasive attitude will test Sloane as they team up to catch a serial killer. They first have to prove cases are connected, that a serial killer exists and collect legitimate evidence on the suspect. Then it’s a harrowing race against the clock to prevent further murders. You’ll wonder if Gwen’s delusional, if Sloane has set herself up to get fired or if their theories are even probable. Circumstantial evidence and hunches are not the same as legally proving criminal actions. It certainly kept me guessing as I raced through the pages.
This story is completely different from Sloane’s other adventures as this mystery is set mostly above water. It has a gut wrenching plot theme with just the type of scheme vulnerable victims could all to easily to fall for. The scariest part of the book is how plausible the scenario is, how it’s possible this could happen to a friend or loved one.
Thank you to NetGalley for the opportunity to read a digital advance reader copy of “Sea Castle” by Andrew Mayne and to Thomas & Mercer. These are all my own honest personal thoughts and opinions given voluntarily without compensation.
Profile Image for fleurette.
1,534 reviews161 followers
December 7, 2022
A good addition to an excellent series. And a fun book for those who haven't read the previous books in the series.

The body of a young, drowned woman is found ashore on a Fort Lauderdale beach. Sloan McPherson of the Underwater Investigation Unit feels that no one really wants to find out what happened to the young woman. Unable to leave the case unsolved, Sloan seeks help in unusual places. And the story takes a very interesting turn for the reader quite quickly.

This story is a little different from the others in the series. First of all, because Sloan works mainly without the help of her well-known teammates. Of course she can always count on them in the most important and difficult moments. That doesn't mean she works alone. Sloan is helped by Gwen, a legend of the Department and a very expressive character.

This book is also unlike the previous ones because Sloan's investigation is completely different. It is not as strongly connected with water bodies as before. Doesn't mean it's any less interesting. The whole case that McPherson is working on is really nicely twisted. False leads abound. Sloan has to do a typical police job much more than before. And while I may have missed that unique connection to water at times, I believe that in this book Sloan had the opportunity to show her exceptional investigative skills and keen intelligence.

Fans of the series will not be disappointed. And new readers will also get some very good suspense. This book is easy to read without knowing the previous books in the series.

Thanks to NetGalley and Thomas & Mercer for providing me a copy of this book in exchange for an honest review.
Profile Image for Linda.
753 reviews18 followers
March 5, 2023
Calling this a "thriller" is an exaggeration

I hate to say it, but this entry is sadly the worst of the entire series. Though there were a few mild exciting moments that prevented my rating from dropping to 1-star, it still bears mentioning what a severe let-down this story was. It sputtered and choked most of the way through. Frankly, I don't even have the stamina for a good and proper review. It was just THAT underwhelming.

The action was dull, the case uncompelling. There were hardly any thrills to keep me on the edge of my seat. It was tame and ho-hum. And since the UIU was temporarily out of commission for this entry, there was literally no underwater investigating (unless you include the robot). It just made this entire book feel like some elaborate filler, and not the good kind.

It also didn't help that Hughes and Solar, both necessary staples in my opinion, were reduced to background/side characters without the UIU. Once I realize that their minimal scenes were pretty much the most exciting moments this book had, I knew my appreciation of a story without their heavy presence was in trouble. Combine that with a bland story and I knew I would be done for.

If I had to compliment anything it would be writing style and character interactions. I have no complaint about the presentation of the story. The case, despite being dull, had some nice surprises (as well as predictability). But my gawd, the story as a whole was just too tragically boring. However, given the way it ended, I'm hoping things will turn around. Because so far, book #2 wins.
Profile Image for K.
694 reviews8 followers
October 4, 2022
Sea Castle was my first Andrew Mayne read and I really liked it! Fast-paced with a main character (Sloan McPherson) who likes to bend the rules - in this "case" (pun intended), she meets her match in irascible Gwen Wylder. Gwen's been shunted off into no-policewoman's land b/c of her quick temper and accusations of witness and evidence tampering. Gwen throws some cold cases Sloan's way (seems the UIU is on hold at present and Sloan's at loose ends) and together they look to solve the "Lost Girls" case. Very much enjoyed their journey, and a few twists and BIG turns along the way make it super fun. The last few chapters really pack it in; in fact, I'd say the first 2/3 of the book are a bit slow. Still a winner, though, and now I'm interested in Mayne's entire catalog. Love it when that happens!

P.S. Thanks to #netgalley for the ARC.
Profile Image for Roxanne Spencer.
393 reviews5 followers
October 9, 2022
The Underwater Investigation Unit has been temporarily (at least that's Sloane's hope) disbanded, and Sloane has been seconded to the Florida Department of Law Enforcement. The FDLE isn't prepared for her investigative prowess and she soon finds herself working with a curmudgeon buried in the basement of the Miami PD, Gwen Wylder. Sloane's unconventional approach soon provides new leads in two cold cases, and she's soon pulled along on a crazy ride to prevent a murder! Great fun as usual.

Thanks to Thomas & Mercer for access to a digital ARC on NetGalley.
Profile Image for Lori L (She Treads Softly) .
2,949 reviews117 followers
February 16, 2023
Sea Castle by Andrew Mayne is a very highly recommended procedural/psychological thriller. This is the fourth novel in the Underwater Investigation Unit series which also includes The Girl Beneath the Sea, Black Coral, and Sea Storm, but it can most definitely be read and relished as a stand alone novel.

Police forensic diver Sloan McPherson of the currently inactive Florida Department of Law Enforcement Underwater Investigation Unit is called in to assist when a young woman's body is discovered on a Fort Lauderdale beach. Floating near the body is a bag containing the woman's clothing. Sloan is positive it is murder and the dead woman, identified as Nicole Donnelly, was strangled. The rest of the team of investigators have questions and doubts after the autopsy. Sloan decides to pursue the case, which leads her to Gwen Wylder.

Gwen is a rude, obsessive, intelligent Miami homicide detective. While she looks at Sloan's case, she demands Sloan look at two different cold cases she is investigating. As Sloan looks into the cold cases and finds new clues and answers, another woman disappears. Sloan and Gwen form a fractious partnership trying to find the person who is killing women.

Sloan and Gwen are both wonderfully strong and fully realized female characters. Their backgrounds are explored within the plot and the development of their characters continue throughout the novel. As the narrative progresses there is a character presented that will confound and throw most readers off course.

The writing is excellent in this fast-paced engrossing procedural that reads like a psychological thriller. I absolutely loved this entertaining and gripping novel and need to look at the other books in the series. The twists and new revelations in the plot are focused, surprising and unique. I found myself glued to the pages and totally immersed in the story. Even though there isn't a lot of underwater investigation in Sea Castle, there is still a fascinating and exciting investigation related to the ocean. The final denouement was a surprise and unexpected. Sea Castle is an outstanding novel with a captivating narrative!

Disclosure: My review copy was courtesy of Thomas & Mercer via NetGalley.
http://www.shetreadssoftly.com/2023/0...
Profile Image for Michelle.
382 reviews20 followers
February 18, 2023
Sloan McPherson, a Florida police diver with the now disbanded Underwater Investigative Unit, has been temporarily reassigned to a land-based unit, and when the body of a young woman is found along the shoreline, Sloan is called in to consult. Even though her colleagues are eager to write this off as an accident or suicide, she suspects murder, so she reaches out to a cantankerous homicide detective with a reputation for volatility to help her prove it.

The main reason I enjoy this series so much are the tense spots Sloan and her team mate Scott find themselves in when they dive, so I was disappointed that this took place almost entirely on land. That being said, this series has great characters and it’s well written, so I still enjoyed this book, and the author teases that Sloan and her UIU team mates may be back together and in the water in the next installment, so I’m looking forward to that!

Thomas & Mercer via NetGalley kindly provided me an ARC of this book in exchange for an honest review.
Profile Image for Maria.
1,199 reviews15 followers
July 19, 2023
Phew, that ending restored my faith in the series.
Because while I do love spending time with Sloan just for the sake of her solving crime - I did think the things that makes the series unique (the ocean and the diving) were sorely missing from this particular book.

Don't get me wrong - it was still a good book and mystery!
Especially Gwen was particularly entertaining. I ended up loving almost every scene including her sometimes erratic and completely mad character. She made things VERY interesting!

Sloan solving multiple cold cases was a nice touch and change of pace too.
I found it amusing how easily she handled everything Gwen threw at her - even if she surely wouldn't call any of the deeds "easy". 😆

I'm really enjoying the action-filled pace of these books. Can't wait for the 5th!
Profile Image for Madeline.
101 reviews5 followers
April 24, 2023
Wow. Mayne has done it again. In less gory fashion this time but the plot was so thick the need for gore wasn't necessary. The book and chapters were so well-paced and made me want to read more and more, each tantalizing the reveal of another secret that I couldn't put down until I had finished. I haven't read a good mystery in a long time and this most certainly brought me back to the good days of swirling secrets and twisty plots. I will say I was disappointed that Sloan wasn't caught up in a life-threatening situation but then again, the poor woman has been through enough in this series lol. the plot twist at the end was plenty sufficient for me. Kudos to Sloan and the UIU team- loved reading another mystery to life.
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