The ocean can be a scary place with its dark, deep, and unknown depths.
According to Oceana.org, more than 80% of the ocean remains unexplored. It's no wonder that so many people have thalassophobia, or a fear of the ocean.
From abandoned ships and ancient sea monsters to deep-sea expeditions and creatures lurking in the darkness, ocean horror taps into some of our oldest fears: the unknown, isolation, and what might be waiting below.
Welcome to "Under the Sea," the Aquatic prompt in the Scaredy Cat Reading Challenge, a year-round horror reading challenge created for readers who love exploring every corner of the horror genre.
If you're searching for the best ocean horror books, underwater horror novels, or stories about terrifying creatures from the deep, these books deserve a place on your TBR.
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This post is part of the Scaredy Cat Reading Challenge, a year-round horror reading event featuring prompts inspired by monsters, subgenres, and spooky settings. Browse all of the prompts to discover your next terrifying read.
What Is Ocean Horror?
Ocean horror (sometimes called nautical horror or underwater horror) explores the fear of what lives beneath the surface.
These stories often feature:
- Deep-sea exploration
- Sea monsters
- Haunted ships
- Shipwrecks
- Isolated islands
- Mermaids and sirens
- Ancient underwater mysteries
- Claustrophobic underwater settings
Whether the threat is supernatural, biological, or simply the unforgiving power of nature, the ocean provides endless opportunities for unforgettable horror.
Ready to take the plunge?
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Here are 18 Ocean Horror Books for the Scaredy Cat Reading Challenge
into the drowning deep by mira grant
A boat filming a mockumentary in the Mariana Trench is found floating drenched in blood. They send another ship seven years later to discover what happened to the original crew.
Ariel has teeth, lots and lots of teeth.
The Mariana Trench strikes again, this time as the only possible cure for the 'Gets a strange plague reeking havoc on humanity causing forgetfulness and the eventual loss of autonomous bodily functions—you know like breathing. (You need that.) Topside, communication with the underwater research station is lost and a few souls brave the Deep to discover what happened.
sea sick by iain rob wright
Groundhog's Day meets Outbreak on a cruise liner.
Where's Bill Murray or Dustin Hoffman when you need them?
THE FISHERMAN BY JOHN LANGAN
The Fisherman is a memoir of two widowers, both grieving huge losses, as they go on a fishing trip to Dutchman’s Creek, located in the Catskill Mountains. They stop at a diner and rando dude who tells them the story of Dutchman's Creek and begs them not to go. Honestly, it sounds like a huge snooze fest until you get that it's a bizarre and extremely violent alternate reality with monsters, the undead, and a god-like being granting bad wishes like a psychotic genie.
The Swarm by Frank Schätzing
Alien lifeforms called the Yrr are influencing the oceans' creatures to rebel against mankind as payback for the way we have treated nature. It's probably a pretty good read but I can't get past the fact that they are all called the Yrr.
Alien pirates? Yrrr!
Sphere by Michael Crichton
More of a sci-fi thriller than horror, Sphere is about finding a presumed alien vessel (obviously sphere-shaped) on the seafloor and they send down scientists to investigate. Lesson learned: if Dustin Hoffman shows up, run.
DEAD IN THE WATER by Nancy Holder
The shipwrecked, vacationing passengers of the ill-fated freighter, Morris, are picked up by the H.M.S. Pandora and sail into a cruise of metaphysical terror, madness, and death.
That's it. That's the whole synopsis. You're welcome.
The Meg by Steve Alten
That damn Mariana Trench again. Not killer mermaids or a forgetfulness virus. This time we get a big ass shark, the Megalodon. Spotted by a Navy diver on another mission, dude freaks out—understandably as I think we all would upon seeing a big ass shark (and some of us seeing any ass sharks. Me. I'm talking about me.) No one believes him because they are extinct. Duh. Because he's not very smart, he goes back in the water and they start believing him when people are getting crunched. They spend the rest of the novel trying to make it go kaboom. However, like Sharknado, there is a sequel...and another...and another...and...another.
The Deep by Alma Katsu
Weird shit happens on the Titanic and true to history, this version sinks too. A maid survives the sinking and after a brief stint in an asylum, decides to go on its sister ship turned medical hospital, The Britannic, with absolutely no medical training because why the hell not? Is Annie the maid crazy or is there something supernatural going on here? At least we won't have to argue that Jack could have fit on that door with Rose.
tidepool by nicole willson
Sorrow's brother Henry disappears, so off she goes to the small seaside town of Tidepool to find out what happened to him. First off, who names their kid Sorrow? That's just setting her up for failure, and that's before the bodies start washing up looking like chew toys for giant ocean monsters. This is the kind of book where you constantly scream at the protagonist to get the hell outta dodge, but instead they say "You're not my mom" and stay.
Flowers for the sea by Zin E. Rocklyn
Stuck on a boat surrounded by air and sea monsters, survivors of a flooded kingdom are struggling to exist. One of them, a woman named Iraxi, is extremely pregnant and, like most pregnant women, doesn't really want to be pregnant anymore except for very different reasons. She resents everyone, including her unborn er, thing. The ship reeks, the people reek, and being pregnant also reeks.
This anthology is part of Eerie River Publishing's It Call From series with "twenty brutal tales of horror from the deep blue sea." There's killer kelp, menacing mermaids, elder gods, family curses, and all things in between.
the kelping by Jan Stinchcomb
The Kelping by Jan Stinchcomb is number nine in Unnerving's Rewind or Die series. Those of you expecting a horror-filled flesh-eating mermaid tale might find it a little tame. What's inside these 67 pages is a more insidious tale of mermaids infiltrating a sleepy little seaside town.
Saltblood by t.c. parker
People are shipped off to an island with a Faraday cage prison to reflect on being trolls on social media. It's a peaceful place, except for—you know—the whole evil monster bit.
The Devils shallows by Debra Castaneda
Salt marshes are weird places anyway but add an urban legend about the Slough Devil and it's extra weird. Adam doesn't believe in monsters, but that's okay, the monsters still believe in him.
sea witch by Sarah Henning
Now we get to the Little Mermaid retellings. C'mon, I had to toss a few in.
Set in 1860s Denmark, Evie (the witch) meets a mermaid with the face of her dead friend. They fall for a couple of princes and Evie has to help her new friend keep her legs. Life's full of tough choices, isn't it?
Drown by Esther Dalseno
Sticking more closely to the original by Hans Christian Andersen, this one is dark as it should be. No singing or friends named Flounder. Matter of fact, a girl has no name...nor does anyone else. It's just The Little Mermaid or The Prince.
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Continue the Scaredy Cat Reading Challenge
Finished your journey beneath the waves?
The Scaredy Cat Reading Challenge is designed to help horror readers explore every subgenre, from haunted houses and witches to ecohorror, gothic fiction, and supernatural terror.
Choose your next prompt, discover a new favorite author, and keep building the ultimate spooky TBR.
Still chasing the unknown? Try these eerie prompts next:
🌿 Feed Me, Seymour — Ecohorror where nature turns deadly.
🏰 Crumbling Castle — Gothic horror with isolated settings and creeping dread.
😈 Let's Summon Demons — Supernatural horror full of possession and ancient evil.
🌕 Howl at the Moon — Creature horror featuring cursed transformations and savage monsters.
Just remember... sometimes what's beneath the surface is best left undiscovered.