SEQUEL TIME! Sequel time is never a good time in Goosebumps land...
Billy, Sheena, and their scientist uncle (SO MANY SCIENTISTS IN THIS SERIES) are back on the water, and who the hell cares that they discovered mermaids last book. We're going to talk about PLANKTON. For serious. Well, at least until the kids start seeing GIANT fish swimming around. In fact, when Billy's goldfish explode in size, they almost sink the ship! This causes some really bad dudes to come by who have been experimenting on the plankton to grow super large fish to save the world from hunger, but they're evil and don't want people to know because reasons. They are going to kill our protagonists, but they escape thanks to GIANT seagulls and end up on a deserted island until they are rescued by GIANT dolphins. The dolphins bring them back to their ship where the head evil dude is. He reveals that when a human eats the plankton, they turn into a fish. Billy tricks him by drinking some by not changing (but it was totally cause he had an "awesome" prank involving ice tea prepared), so the evil dude drinks some himself, becomes a fish, and YEA THIS BOOK IS FINALLY OVER EXCEPT SHEENA MIGHT BE A FISH I DON'T CARE. Deept Trouble II made no sense, wasn't scary, and completely ignored what happened in book 1. BAD BOOK, GO GET EATEN BY A GIANT CRAB OR SOMETHING!