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The Mermaid Hypothesis

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Fish are not great conversationalists. That’s not why Niua sneaks aboard a research ship, or why she’s stumbling around on legs, pretending she’s not a mermaid, but years of living among uncommunicative sea life may explain why she’s unwisely flirting with a marine scientist who’s far too perceptive--and far too female--for Niua’s safety. She needs to focus, but Ms. “Why Aren’t You on the Passenger List?” keeps distracting her. In the best possible way. She’s in over her head, and she doesn’t have time to waste. She has a shipwreck to find, a treasure to reclaim, and a secret to protect. Before mermaids disappear forever.

199 pages, Kindle Edition

Published October 25, 2022

28 people are currently reading
55 people want to read

About the author

Siri Caldwell

9 books15 followers
Siri Caldwell does not believe in waiting for frogs to turn into princesses, because frogs are cute the way they are. Her fun lesbian romance novels have finaled in the Lambda Literary, Golden Crown Literary Society, and Rainbow awards.

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5 stars
60 (54%)
4 stars
34 (30%)
3 stars
14 (12%)
2 stars
1 (<1%)
1 star
1 (<1%)
Displaying 1 - 12 of 12 reviews
Profile Image for AnnMaree Of Oz.
1,510 reviews131 followers
January 25, 2023
Kindle Unlimited.

A very good mermaid sapphic tale (or tail? lol) Sweet, hot and sassy interactions between our hidden mermaid and the scientist who is not sure what to make of her.

I would have liked more depth for both characters and the situations they were in. It never really felt as meaningful nor as 'urgent' as it was meant to.

It's a quick story, fast paced, but there are times I wish it could have slowed down so we had a chance just to get to know our characters, and their compatibility beyond sex, because the I Love You's came too quickly.

Still a good story I would recommend. I'm a sucker for mermaids!
Profile Image for Lexxi Kitty.
2,060 reviews477 followers
December 14, 2022
Fifth work I've read by this author. I was going to say 1 short novel & 4 full length, but this book here is only 80 pages longer than that 119 page short novel. First two books I'd read by this author I'd given 5 stars to (well, 4.9something & 5+), and the other two were solid-ish 4 star works.

First two 5 star books were also fantasy's, while the other two were not. Not sure if that means anything that I ended up giving this one here 5 stars and it also falls into the fantasy category. Probably does mean something.

Never really expected to read another book by this author, since their previous works came out 2013-2017 (other than a nonfiction book that came out in 2020). Super glad another one came out, and when I spotted it - I bought it immediately without even looking to see what the book was about (which is how I also happen to own that nonfiction book, which I haven't actually read because, well, nonfiction).

So what's this one about? Mermaids. And a science expedition that runs into one.

Book opens with Niua at the POV controls, and is one of the two POV's in the book. Niua is a mermaid that has learned about how one of her people's artifacts still exists and where she might be able to find it (in a ship wreck), so climbs aboard a particular ship while it is exploring a region. Whereupon she meets the other main character, Mallory.

Mallory is one of the scientists aboard "The Sea Monster" (the name of the ship). One who is super interested in examing the rocks dredged up by the ship. For science reasons. Plays a part in the story, but the story is much more about the interaction between Mallory & Niua. Who move from a hostile "who are you, how'd you get aboard this ship" relationship to . . . well, a relationship.

Lovely book. Loved what I read. I'd recommend this book. Um. hmm. Yay? Hehe, I'm not sure what else to write. Well, there was one thing but . . ..

That nonfiction book? While I haven't read it, I assume it has something to do with writing book descriptions. And blurbs. Since that's the title of the book. Which I mention because the book description for this one probably would not have lead me to buy this book. Or, in other words, if not for the fact this was an insta-buy, the book description would not have lead me to buy this book. Why? Because it's a jumble of words without any paragraph breaks (the "about book" section inside the actual book is much better about pargraph breaks and stuff, but ...), and makes zero mention of Mallory's name. She's in there, as a marine scientist, as "Ms. “Why Aren’t You on the Passenger List?”". But no name.

Right. Weird thing to focus on. Back to: loved the book. Is super short. I'd recommend it.

Rating: 4.98
December 14 2022
35 reviews
March 1, 2023
Perfect holiday read

What’s not to love about an alluring mermaid and one misfit scientist, who doesn’t seem to get why all the men on the scientific expedition don’t understand that a woman suddenly appearing, literally miles from anywhere, isn’t suspicious? And why, is Niua here at all? And what is she hiding? And why is she so mysterious?

And doesn’t the, not knowing, just intrigue the hell out of poor Mallory’s scientific mind… it’s nothing more that surely? Because Mallory is done finding romance but what if, it finds her in the shape of magical mermaid?

I loved this and thought they were just so cute together. I totally loved the suspicious, sometimes grumbly scientist and the equally alluring mermaid, who is on a quest to find a long lost treasure, regardless of the danger it puts her in.

The storyline moved very well and was quite an enjoyable, an entertaining read that made me smile and I would recommend it for that perfect holiday read. I did. And if you happen to be near the ocean with the scent of brine in air…. all the better. I hope you enjoy it. I did.
304 reviews2 followers
July 30, 2024
I read this for a reading challenge but found that I really enjoyed the story and it’s telling. The two MC’s were both appealing in their own ways, Mallory with her surly scientific mind and Niua, the mermaid able to charm men (but not women) with just a look into their eyes. Although the time frame in this is fairly swift it felt like a slow grow romance as both fall for the other and as Niua’s secrets are gradually revealed. They think a future for them is impossible, but who knows what the future holds? Both have had a series of disappointing romances where they proved not to be enough (or too much) for their previous lovers. But together they are perfect.
I’m not going to spoil things by telling how they solve their conundrum, suffice to say this was rather delightful and left me feeling ‘Awwwww…cute!’
10 reviews
May 28, 2023
Shockingly Good

Honestly, I have lower standards for books in more niche genres with small numbers of reviews by authors whose works I haven't read. But this novel is great, even by my regular standards.

Amazing chemistry between fascinating and believable characters with realistic, heartrending struggles. Top notch editing - I didn't find a single mistake in the entire novel. I really felt great sympathy for Mallory's plight as a woman in a very technical field of science. And that's another strength of the novel - delving deep into that branch of science in a way that's relatable without being overly simplistic.

If you like mermaid stories, romance stories, or lesbian fiction, you'll love this.
Profile Image for Issy Waldrom.
Author 10 books55 followers
November 1, 2023
A mermaid seeking a stolen treasure, and a scientist who might be a little more than tempting...

I really enjoyed this story. It's a sweet romance, rather than a monster one, Niua trying to locate the site of a sunken ship, and finding herself become than a little attracted to Mallory, with the scientist warming up to her as well. They dance around each other a bit, getting drawn together, and honestly it was rather adorable.

It's an engaging story, well written and paced, and I really liked how it concluded. Definitely recommend.
Profile Image for Victoria.
228 reviews6 followers
June 4, 2025
It's not groundbreaking or anything, but I always appreciate a mermaid story that doesn't end with the mermaid becoming human. However, unfortunately, like most mermaid books I've read this one avoids the question of sex when in mermaid form. SMH, why is published fiction always so behind fanfic.
Profile Image for Cara Ramsey.
Author 2 books5 followers
July 9, 2023
A Fairy Tale of the Sea

Fantasy romances tend not to grab me that often but this one made me laugh, smile, and in the end, cheer for the impossibility they needed for everything to work out.

Recommended!
Profile Image for Mal.
200 reviews1 follower
April 26, 2024
this book was so amazing!! this is truly a hidden gem the relationship with the two girls was so fun to get behind and just a really really fun quick read. It's lacking a little bit on the plot side but the smut scenes make up for it imo 🧜‍♀️

plus one of the main characters has my name!
Profile Image for 3DKing.
275 reviews1 follower
July 5, 2023
4 - Cute, simpel, wholesome. It's a really nice little story about a mermaid and a scientist, about mermaid-history, overcoming some fear and about curiosity.
Profile Image for Em.
42 reviews
June 14, 2025
This was an interesting book. I really liked the take on mermaids and thought the concept was fresh. That said I think the story spent a little too much time in a slice of life mode aboard the initial research ship. It slowed things down more than it needed to.

Overall I was satisfied with how everything played out. The ending worked and the ideas behind the story were strong. I just wish it had moved a bit faster to get there.
Displaying 1 - 12 of 12 reviews

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