- Giant Enemy Crab
Really big crabs. Well, other crustaceans, too. They all taste a lot like crab, though.
- Giant Squid
Really big squid. Older Than Feudalism, they have the benefit of actually existing. Makes great calamari.note
- Kraken and Leviathan
The epically scaled, humongous world-ending dwellers of the deepest trenches, often with lots of references to Lovecraftian or Biblical beasts. Tastes like whale meat.
This prehistoric beast is great for those who like to buy their Shark Fin soup in economy scale.
- Stock Ness Monster
Those that ape (or more like serpent) the queen of cryptozoology, her royal slitherness the Loch Ness Monster. Said to taste rather exotic, like crocodile meat.
- Turtle Island
Those whose large size combined with a sedentary life in shallower conditions make them liable to be confused for islands. Apparently the taste of giant turtle is meant to be greater than any chicken, beef, mutton or butter and a favourite for long sea voyages.
open/close all folders
- A series of Jameson Irish whiskey commercials feature John Jameson jumping overboard to retrieve a barrel of booze. A giant octopus is seen reaching towards him underwater in some versions. Viewable here.
Anime & Manga
- The Dragonosaurus from a Crossover movie featuring characters and Humongous Mecha from Mazinger Z, Great Mazinger, UFO Robo Grendizer and Getter Robo was a real weird, gigangic sea monster. Its body was a gelatinous, amorphous blob with a face on it, and several snake-like heads sprouted from it. It was told it was a -formerly believed extinct- Prehistoric monster had mutated cause oil spills polluting the ocean.
- The Three-Tails and Eight-Tails from Naruto, a giant turtle-crab creature with water-based powers and an ox-like kraken monster, respectively.
- There's also a giant squid that was the guardian of an island where Killer B and A trained.
- One of the magical creatures in Magical Girl Lyrical Nanoha from which the Wolkenritter took Mana was a many-eyed giant sea monster that emerged from a whirlpool.
- One Piece, being a pirate-themed adventure, has lots of sea monsters — the sea kings being a pretty prevalent example. They, along with a lack of winds, make it nearly impossible to enter the Grand Line from anywhere but the entrance.
- And to put an image in mind, Sea Kings can rival the size of islands in size and usually attack whatever they see.
- Digimon has an entire group of digimon devoted to this. Of particular note are the Seadramon family, which includes the season one baddie Metal Seadramon, and the enormous Demon Lord, Leviamon.
- Water Pokémon. Let us see, we have giant crabs (Kingler), giant lobsters (Crawdaunt), giant jellyfish (Tentacruel, Jellicent), a mini Loch-Ness monster thing (Lapras), a large sea-horse that whips up whirlpools by snoring (Kingdra), giant clams (Clamperl and Cloyster), a torpedo shark (Sharpedo. Yeah.), a blimp-like whale (Wailord), ancient water animal and plant things (Lileep, Anorith, Relicanth)... and the waters hide many, many more.
- Other notable examples include killer crocodilians (Feraligatr), artillery wielding cephalopods (Octilliry), various kinds of sea dragons (Gyrados, Milotic), various denizens of the deep (Lanturn, Huntail, Gorebyss), and the creator and master of the seas of the Pokemon world (Kyorgre)!
- Also, in one episode Team Rocket accidentally created a giant Tentacruel, with what they believed was a poison. Misty had to convince it not to destroy a city.
- The monster in Junji Ito's "The Thing that Drifted Ashore" looks like a combination of an eel, a mass of barnacles, and the nightmares of everyone in the world who suffers from thalassophobia. It's implied to be far from the worst thing out there.
- Giganto/Monstro, the Sub-Mariner's giant whale with arms and legs in Fantastic Four.
- A sea serpent appears in The Sandman story "Hob's Leviathan", part of the "World's End" arc.
- So are the oceans and rivers of Elekton in The Trigan Empire
- The oceans of Skataris are filled with monsters in The Warlord.
- Children of an Elder God: In chapter 4 Asuka fought Amaliel, an aquatic, sea-dwelling monster resembling a viscous blob with tentacles and pincers.
"...an almost globular torso, with six long sinuous limbs terminating in crab-like claws. From the upper end a subsidiary globe bulged forward bubble-like; its triangle of three staring, fishy eyes, its foot-long and evidently flexible proboscis, and a distended lateral system analogous to gills, suggested that it was a head."
- Aska has the Jormungand itself.
- Embers: Man-eating Seahorse dragons, leeches that can give hell to the Unagi, and (by chapter 43) something huge that makes Sokka think twice about pentapi. All stem from the Ocean Spirit's ongoing revenge, and they probably aren't the only things that we'll see.
- Add to that list the Isonade, or shark monster, that Azula faced as she was battling with Makoto.
- Walking Whales, a.k.a. the Kadzait. They can grow to huge sizes (the skeleton Zuko encounters is 50 ft. tall), live extremely long lives, and can be good or evil, just like dragons. The Dark ones are known as Sea Serpents.
- In Chapter 78 Zuko defeats a sea serpent banished from his clan for cannibalism of the pods' children. In Chapter 79 we find out that Kadzait are usually sable in color and like colder waters. They have much smaller and more brightly multicolored cousins who live in warm waters called Rakko. The Kadzait seem most like whales while the Rakko are like dolphins.
- Considering that "rakko" means otter in Japanese, it's likely that the Rakko are otter-dolphin hybrids, following the combined-animal theme of Avatar.
- One World: Quite a number appear in the story, ranging from the dragon-like Knucker to the mythical Kraken of the north sea.
- The Beast from 20,000 Fathoms, a giant dinosaur-like monster that emerged from the sea after thawing out of an iceberg.
- Jaws and its host of imitators.
- The bluntly titled Godzilla Vs. the Sea Monster, where the King of the Monsters faces off against Ebirah, a giant crustacean monster..
- Heck, Godzilla himself certainly applies. In the first film, he's even shown sleeping underwater. Godzilla (2014) reinforces this aspect of his nature by having the rapid-fire opening credit sequence juxtapose antique artistic depictions of sea monsters in books and maps with Retraux footage of Godzilla swimming around in The Fifties.
- Likewise, there's Manda, who is a sea-dwelling Chinese Dragon-looking guardian of the lost civilization of Mu.
- There's Always a Bigger Fish on Naboo. First, there's the Opee Sea Killer, a bizarre fish-crab hybrid that eats with a long, sticky tongue. Then, there's the larger Colo Claw Fish, a giant sea serpent with clawlike appendages used to capture smaller creatures (including baby Sea Killers, which can however chew out of a Claw Fish's stomach to escape). And finally, there's the Sando Aqua Monster, the biggest predator in Naboo, who can and will eat almost anything (including the aforementioned Colo and Opee) that stands in its way.
- The Kaiju in Pacific Rim, which emerge from a rift in the middle of the Pacific and swim towards major human cities. The last batch that guard the Rift in particular seem specifically designed for underwater combat.
- Deep Rising: Features man-engulfing tentacles that act as though they are independent creatures but are, in fact, attached to one giant mutated cephalopod.
- Jurassic World: The Mosasaurus, natch.
- Deep Star Six is primarily about a deep sea construction facility's struggles with an unidentified, armour-plated sea monster, with no perfectly clear analogs to any known sea life.
- The Avanc (from the afanc of Welsh mythology) from China Miéville's The Scar.
- Lord of the Flies also has the whole "beast from sea" speculation affair.
- The Watcher in the Water from Lord of the Rings appears to be something like a giant octopus.
- The sea serpent from Voyage of the Dawn Treader.
- The creature in Ray Bradbury's short story The Fog Horn, which was the inspiration behind The Beast From 20,000 Fathoms.
- In Orlando Furioso, two different women, Angelica and Olympia, were offered to placate two different sea monsters — at least one of which was called an orc. Also, the enchantress Alcina uses a whale as transport.
- Discworld - The illustrated novel The Last Hero features a map of the disk with all sorts of monstrous sea creatures popping up here and there. Then a later illustration shows Mustrum Ridcully fishing... with all those creatures lying in a pile at his feet. Turns out the creatures on the map weren't quite on scale.
- The sentient sea serpents in Robin Hobb's Liveship Traders trilogy.
- In the massive live-action RPG tournament from The California Voodoo Game, the aliens responsible for all the weird events were stranded on Earth because they'd grown into adulthood since their ship crashed. Their mature forms were those of massive flatfishes more than 50' long, so they could no longer fit into their spaceship. Too bad the players never made it back up to the roof, to sneak a peek at the swimming pool....
- Sense and Sensibility and Sea Monsters, which is essentially Sense and Sensibility, except everything in the ocean developed a psychotic hatred of mankind.
- Taylor Anderson's Destroyermen takes this trope to an insane level. In this alternate world, the great white shark is a small predator with loch ness style creatures being average size and everything being dwarfed by the monster fish, a sea creature so ridiculously enormous that it could swallow an aircraft carrier in one bite.
- Percy Jackson encounters the legendary Charybdis and Scylla in The Sea of Monsters, a random sea serpent in the short story Percy Jackson and the Stolen Chariot from The Demigods Files, and sees a whole army of them attack Poisden's forces in The Last Olympian.
- The sequel series, has the main group encounter Ceto, the mother of all sea monsters (though she certainly doesn't look like one when she shows up), and one of her children, the Skolopendra (which is definitely a deadly sea monster).
- During Galaxy of Fear the heroes visit Hologram Fun World and interact with a simulation of a whaladon, which is friendly then but later tries to get them.
- In H.P. Lovecraft's short story Dagon, the protagonist is traumatized by the sighting of a large, unidentified sea creature. In this case the creature itself never actually does anything particularly hostile, it's just the complete unfamiliarity with this being that freaks him out. Lovecraft also wrote the better-known Cthulhu, who would also qualify although he isn't necessarily confined to the sea.
- In one of Dora Wilk Series short stories, Eryk is attacked by some sort of sea serpent which crossed over from its plain into our reality. Szelma has to rescue him.
Live Action TV
- Primeval has featured a few prehistoric sea monsters. Episode 1.3 gave us a Mosasaur, Episode 2.4 gave us a future shark and the Mer, walrus-like sea monsters that appeared to have evolved from primates, and Episode 5.2 gave us a whole pack of Pliosaurs.
- Mighty Morphin' Power Rangers: The Dragonzord is this in robotic form, rising dramatically from the ocean to wreak destruction upon either the city of Angel Grove, or the forces of evil, depending on who possesses the Dragon Dagger, and whether the rightful owner of the dagger is in control of himself. It is a Godzilla-esque metal beast, and of endurance as yet unmatched.
- A sea monster appears on the cover of Asia's 1982 self-titled debut album.
Myth And Legend
- Older Than Feudalism: Charybdis, from The Odyssey, an unseen monster that swallows and spits out the entire ocean on a regular basis in the form of a giant whirlpool. Related is Scylla, who lives near the ocean rather than in it and has lots of heads note
- Another even older Older Than Dirt example: Tiamat, the primordial sea serpent from the Babylonian creation myth Enűma Eliš.
- Many a woman Chained to a Rock was to appease a Sea Monster. From Greek legends, Hesione and Andromeda's monsters. Andromeda's was named Cetus, which of course means "whale" now.
- To add insult to Cetus' mortal injury, after Perseus slashed her throat, he delivered the deathblow by showing him the petrifying head of his own sister, Medusa, transforming Cetus into a coral reef.
- The Con Rit, or Tarrasque, a sea serpent claimed to be found in the South China Sea. Some theories say that the possible sea serpent is inspiration to both the Oriental Dragon, and the South African Snake God. note
- The Kalevala has a giant pike and Iku-Turso, a malevolent sea monster.
- Norse Mythology has the Kraken of course. And then there's Jormungandr, the Midgard (World) Serpent, the sea monster to end all sea monsters. An immense sea snake, he wraps all the way around Midgard, holding his tail in his own jaws. He has a major rivalry with Thor, and plays a key role in Ragnarok.
- Seawitch depict two monstrous sea creatures as war mounts — one is a giant fish with fangs and ragged wings, while the other is a barracuda-like serpent.
- Kaiju Big Battel has Unibouzu, a giant urchin and Call-Me-Kevin, an alien who landed in the ocean.
- Magic: The Gathering has tons of Sea Monsters. Leviathans, Krakens, Sea Serpents, Giant Enemy Crabs, assorted giant fish and whales... notably enough, they're often both blue and absurdly huge, despite the Blue colour being anything but based on brute force.
- Rifts has boatloads of sea, lake, and even river monsters.
- Dungeons & Dragons
- Sea Monsters by the truckload: scyllans, krakens, leviathans, ramfish, dragon turtles, sea drakes.
- And then there's Dagon, a lesser-known demon prince who is an eel with the head of a freaky fish, six tentacles ending in clawed hands, and more eyes than I really want to count. Other demon princes are afraid of him.
- The ocean-oriented Stormwrack book includes many Sea Monsters.
- Older editions had the Behemoth (giant hippo), aquatic "dinosaurs" (Elasmosaurus, Mosasaurus, Nothosaurus, Plesiosaur), dragons (Lung Wang and Yu Lung), Froghemoth, Giant (Crayfish, Crocodile, Eel, Octopus, Sea Snake, Squid, Turtle), giant fish (Afanc, Gar, Pike, Verme), Merrow (aquatic ogre), Mottled Worm (aquatic Purple Worm), Sea Serpent, Seawolf (lycanthrope), and Vodyanoi (aquatic Umber Hulk).
- The Warhammer world has buckets of these, as detailed in the Seas of Blood supplement to the early 90s naval warfare spin-off Man'O'War and the 2011 Pirate-themed spin-off Dreadfleet. Warhammer's giant sea monsters include the classic giant squid Kraken and the horrific Black Leviathan (a humongous deep-sea angler fish that could swallow small ships whole), as well as the Narwhal-like Behemoth, the giant crab Promethean the Sea Dragon, the giant merman Triton, the Sea Elemental and the giant shark Megalodon. Dreadfleet has its own zombie sea monsters - the Sea Giant, Bone Hydra and Leechwyrm - and even a ship made from the rotting undead carcass of an Orb Leviathan (possibly the same species as Man'O'War's Black Leviathan, maybe not). Finally smaller, but still huge, sea monsters are available from Forge World to use in land-based Warhammer armies in the shape of the Merwyrm and its variants, and the Dark Elf army has access to aquatic Hydras and the abyssal tentacled fiend Kharybdis.
- Warhammer 40,000 has a few, though they're rather obscure. The Space Wolf homeworld has a massive kraken (said to be a Tyranid offshoot) and sea serpents straight out of Norse myth, appropriate given the Space Wolves' Viking theme, and a sea monster is said to live on the planet Armageddon, where it attacked Ork ships. Given the nature of the setting, it's a safe bet that most world with any oceans have at least one.
The "Iron Snakes" chapter has a mostly ocean-bound home world (their fortress-monastery is on one of the moons), and one of the challenges which aspirants wishing to join the chapter have to face is single combat with a sea serpent using only a harpoon and a canoe.
- Yu-Gi-Oh! features many sea monster cards. Most notably are Sea Serpents which are a whole monster type, and many Water monsters can count.
- Monsterpocalypse has the Tritons, whose main monsters are kaiju-sized sea creatures.
- The Water Dragon from Ōkami, which turns out to be the king of the Dragonians.
- The Sapphire Drake Bonus Boss of Wild ARMs 4, which the player first sees preying on another sea monster.
- Kyogre fills the 'primal sea monster' niche, while lesser creatures such as Gyarados are based on sea serpents.
- Milotic is considered the benevolent counterpart to Gyarados due to the fact that it's also a serpent, opposite temperament and the fact it evolves from an equally weak Pokemon though it is much rarer.
- Gold/Silver/Crystal features a Red Gyarados (most are blue) rampaging in a lake. In the game a Red Gyarardos evolves from a Golden Magikarp.
- While not itself a Water-type, Lugia, known as the Diving Pokemon, resides deep within the seas of the Whirl Islands and is said to be the "guardian of the seas." It has the ability to control the weather, most notably it can calm and give rise to storms.
- The Sega arcade shooter The Ocean Hunter has its share of giant sea creatures, the biggest of which serve as boss and mini-boss fights.
- La-Mulana is maybe the only video game to use the Babylonian interpretation of Tiamat (fierce ocean goddess) rather than the Dungeons & Dragons interpretation (five-headed dragon queen).
- Team Fortress 2 - The Demoman considers the Loch Ness Monster to be his mortal enemy, and he accidentally killed his adoptive parents in an attempt to blow it up.
- Del Lago from Resident Evil 4 resembles some kinda giant newt.
- Banjo-Tooie - The boss of the obligatory underwater level is Lord Woo Fak Fak, a gigantic lanternfish who literally lives in Davey Jones' Locker. He can be a bit tricky, but is much easier to fight if you use the Submarine transformation.
Also in Jolly Roger's Lagoon is a giant fish that swallowed Merry Maggie the barmaid. Strangely, it doesn't try to attack you, even when you knock all the teeth out of its mouth in order to rescue her.
- There are some large aquatic creatures in World of Warcraft. Notable examples include Ghaz'rankha, a giant hydra that's a boss in Zul'gurub raid instance (gaint hydras also appear as bosses in Zul'zarrak and the Underbog), and The Lurker Below, a boss in Serpentshrine Cavern raid whose ingame model is actually called "kraken". Some of the larger naga may count for this trope too, their queen Azhara most certainly does.
Hydra in World of Warcraft are lizards with three heads. They have two legs and a heavy tail, so they basically move on a tripod as well. Normal ones are about the size of a wooly mammoth or so, but bosses are a little bigger. The Lurker Below is big enough to be a genuine kraken, and three other things in the game share its same ingame model: two similar wild animals related to specific quests and a sea goddess.
- Every creature in [[the The Aquatic Adventureofthe Last Human aquatic Adventure of the last Human]] is this
- Kraken herself shows up as a boss in a few Final Fantasy games. Final Fantasy X also features a few since your characters are now able to fight underwater. Geosgaeno who is one of the first fiends you fight definitely qualifies - he's a Bonus Boss later in the game. The Giant Flyer Evrae turns into this the second time you fight him, though he's also a zombie. There's also a couple of Sinspawn fiends that you have to fight underwater.
- Super Mario
- Super Mario 64 introduced Unagi the giant eel note and the Sea Dragon — who actually lived in an underground lake. The Sea Monster's name is "Dorrie", although in Japanese it's name is "Doshi", which is a parody of the Loch Ness Monster and Yoshi since the nickname "Nessie" in Japanese is "Neshi".
- Super Mario Sunshine had a boss named Eely-Mouth, who was more goofy-looking.
- Niptra of Arcana Heart, an ancient fish that became the largest and wisest fish in the seas through cycles of reincarnation before finally becoming the Arcana of Water.
- The Shiguras from Dark Cloud 2, extremely reminiscent of Pokémon's Lapras. Dr. Jaming intends to use them as tools for his own nefarious purposes, and goes as far as to enslave one of them, Pau's friend, Shingala.
- Aquanaut's Holiday has several whales swimming in its oceans, but there's also an enormous prehistoric fish floating in the southwest corner of the map.
- Monster Rancher had the Zilla, a freaky whale/gorilla hybrid.
- And Lesione, which is a much cutesier Plesiosaur-like creature with elements of trained marine mammals.
- Morpheel in The Legend of Zelda: Twilight Princess
- One of the later puzzles in Azada: Ancient Magic requires you to free the Baron (Munchausen) from a giant sea monster's mouth.
- Monster Hunter Tri features new mechanics which allow your character to swim and fight underwater. Obviously this has introduced a whole slew of new aquatic monsters including a lightning-spewing serpent/crocodile mix and a large, grotesque Angler Fish capable of perfect camoflage, blinding flashes of light and inflating into a spined ball. There is also a Elder Dragon that is a football field long, and causes earthquakes with it's horns.
- A boss in Metroid: Fusion is Serris, a sea serpent capable of Super Speed.
- Shadow of the Colossus features two: the electric eel colossus that is frankly terrifying, and the wading lake monster, which is terrifying AND frustrating.
- Endless Ocean: Blue World features several prehistory-dating creatures to be encountered, one of whom even tries to attack you. There's also lots of benign marine life which have monster-esque names, such as a large giant squid named "Kraken Jr." and an albino sperm whale named "Leviathan". Sadly, all of the prehistoric creatures are relegated to cutscenes only and cannot be swam with.
- Actually, Kraken Jr. is the giant squid's child - he's actually quite small, but he may still count since he'll eventually grow into a giant.
- Expansion packs for the original Zoo Tycoon allow you to raise and exhibit plesiosaurs and Loch Ness Monsters. Not together, though: they eat each other's eggs!
- Tradewinds: Legends and Odyssey have several sea-monster battles, both bosses and random encounters.
- Also, in the Legends Captain's Log: "Fought kraken. Looking for good calamari recipe."
- Cobra Triangle featured several different sea monsters to include a Giant Enemy Crab, a Giant Squid, sea serpents and giant shark as the final boss.
- In the third chapter of Grim Fandango, Manny ends up on the bottom of the ocean, which is pitch black except for a single light source. Upon finding another traveler, trying to walk to the other side of the ocean(and failing at it by walking in circles for years), Manny gives him a warning.
Manny: Watch out for sea monsters.Chepito: Oh, these guys?Chepito shines his lamp at the ocean, revealing wall-to-wall, creepy-looking sea monsters just behind the darkness. The darkness you are walking through. Try not to think about that during your remaining time under the ocean.
- This is the entire point of the World Monster Fishing mode of Big Ol' Bass 2, an obscure but awesome fishing game. You can catch everything from bass with the American flag colors to a trout with the Mona Lisa on it, from a shark with a leopard design to Dinosaurs.
- The Elder Scrolls IV: Oblivion has the Giant Slaughterfish.
- In The Sims 2, in Neighborhood View, a sea serpent would sometimes be seen randomly at the end of the river (near Gunther Goth Highway) and disappear into the bay.
- Sunless Sea has a lot of these living in the dark waters of the neath. Most of them are bigger than your ship. And then there's the Eye, which either belongs to an enormous one of these or something far, far worse.
- Avatar: The Last Airbender
- There is a reason that the Serpent's Pass was called such, which the characters find out first hand when the giant sea serpent came out when they tried to cross.
- The giant lion-turtle with an island on its back.
- And the Unagi that lives near Kyoshi Island.
- During the Season 1 finale, the ocean spirit assumes the form of a huge, humanoid, Godzilla-esque monstrosity.
- Cecil the Sea-Sick Sea Serpent from Beany and Cecil
- Bad guy Dishonest John had an undersea craft disguised as a giant cephalopod, known and feared far and wide as Billy the Squid.
- Care Bears had a sea serpent named "Shaky" who needed work on his confidence.
- Catscratch features a Kraken, which Gordon must fight in order to wish for a longer tail.
- The giant Nautilus of Cybersix. She beats it by dropping a bridge on it, literally.
- The pilot of The Drinky Crow Show involves whales, which is appropriate because it's set on a whaling ship. The whales are drawn in the style of those really old maps with "Here be dragons" written in the corners.
- DuckTales: The sea monster that ate Scrooge McDuck's ice cream is actually a submarine colored to resemble an orca.
- My Little Pony: Friendship Is Magic features Steven Magnet, an Ambiguously Gay river serpent whose hysterics over having his "look" ruined by the lost of half his mustache cause our heroes a problem in the second episode. In "Slice of Life", he even refers to himself as a "sea monster" — despite having only been seen in a river.
- Spongebob Squarepants: When Spongebob yells that there are sea monsters on the beach to keep people out of the water, an erudite serpent reminds him that "we sea monsters have made great strides in the fields of science and literature."
- In Star Wars: Clone Wars the Mon Calamari fought the separatist forces with knights riding on giant eels.
- Star Wars: The Clone Wars: In the episode Bombad Jedi, Jar-Jar made friends with a Kwazel Maw, a giant, aquatic centipede-like beast native to Rodia. Technically a Swamp Monster, but Rodia's swamps are so wide and deep they're effectively a freshwater ocean.
- Yellow Submarine had a Sea of Monsters.
- Unsurprisingly, the world of Mer featured in The Pirates Of Darkwater is full of Sea Monsters, including Darkwater itself, and the huge, serpentine Leviathans.
- And including extinct animals, we have plesiosaurs and similar creatures like the ichthyosaur and mosasaur, and Megalodon, a prehistoric shark the size of a whale. Its modern counterpart may be the Whale Shark, which is thankfully nonaggressive and feeds on plankton. Indeed, so many different creatures like this existed in the past that one can argue that plesiosaurs can't have survived to the present, because the mosasaurs would've eaten them, long before the K-T extinction took down subsequent forms of reptilian Sea Monster. The modern equivalent of Carcharocles megalodon might be the Whale Shark from a size perspective, but in every other respect it's basically a Great White that is... bigger.
- Check out the miniseries Sea Monsters (from the creators of Walking with Dinosaurs) for some of the nastiest aquatic predators ever.
- Pliosaurus. Its teeth are each a foot long.
- The Oarfish: an eel-like fish that can exceed fifty feet long. Harmless, but quite impressive.
- The African country of Burundi is home to Gustave, a well-known man eating crocodile. Gustave weighs in at approximately one ton, is approximately twenty feet in length, and has been known to eat adult hippopotami. Given the number and variety of bullet-shaped scars which cover his body, it's quite possible that he's Immune to Bullets.
- Saltwater crocodiles can be even larger than Gustave. Large adult male saltwater crocodiles can be more than six meters long and weigh more than 2,600 lbs.
- Prehistoric crocodiles were even larger than saltwater crocodiles. Sarcosuchus imperator was around forty feet long.
- Many of them were also fully marine. Plesiosuchus was basically an orca sized marine crocodile that looked like a shark.
- The Bloop, or rather, whatever made the Bloop, an ultra-low frequency underwater sound that matched the profile of a living creature, but not any specific living creature we know. If it did come from a living creature, scientists agree that it would have to be several times larger than the Blue Whale, the largest known animal on earth. Interestingly enough, the signal originated from a point in the South Pacific roughly 950 nautical miles from the sunken home of another large monster.
- Tullimonstrum, a bizarre fossil lamprey from the Carboniferous Period, bears a striking external resemblence to the Loch Ness Monster, except it's barely a foot long and found in North America.
- The Coelacanth is a person-sized carnivorous fish that has been swimming around virtually unchanged for millions and millions of years. It was thought to have been extinct until live specimens were caught in the 20th century.
- The whole point of fishing shows like River Monsters, Hooked, and Monster Fish. Their catches range from the modest (Taimen), to the bizzare (catfishes of the Amazon), to the truly gargantuan in scale (marlins, giant catfishes, and the Mekong Giant Stingray).
- The basking shark, second-largest living fish, can grow up to thirty-plus feet. They also look rather monstrous, cruising through the water with their three-foot mouths. Fortunately for all mankind, they and whale sharks eat only plankton. They are also the source of a few sea monster myths, where the decomposing bodies of these sharks after having beached or caught as by-catch have been mistaken for plesiosaurs.
- Several deep-sea species of shark are also quite large. The megamouth shark grows to eighteen feet in length, and the Pacific sleeper shark can grow to fourteen, though ichthyologists theorize they may grow as long as twenty-three feet. Related to the Pacific sleeper is the Greenland shark. It lives in Greenland and closer to the surface, routinely grows to seventeen feet in length and has been found with parts of polar bears in their stomachs.
- Lion's mane and Nomura's jellyfish can grow to gigantic sizes. The lion's mane can grow nearly forty feet long and the Nomura can weigh over four hundred pounds. Nomura's jellyfish have also marked off an important check on the "to-do list" of most sea monsters; sinking ships, albeit in a passive manner. "Blooms" of these jellyfish have numbered in the thousands and at least one fishing vessel has been capsized after trying to haul up a net full of these jellyfish.
- The largest lion's mane to wash up had tentacles in excess of 120 feet. That's longer than a blue whale, usually considered the largest organism. Now imagine encountering that while deep-sea diving... knowing its transparent, poisonous tentacles are all over the goddamn place in a huge radius...
- Syringammina fragilissima. It's a deep-water denizen eight inches across. It's not very impressive-sounding, but suddenly becomes more so when you find out it's a single-celled organism.
- Livyatan melvillei is named after both the leviathan and Moby Dick via Melville. It earns the name by having the largest teeth of any known organism.
- Several species of pliosaur, including the so-called Predator X, were roughly whale-sized, but with jaws more resembling those of an alligator.
- Several deep sea fish are very bizarre and monstrous in appearance, with huge jaws filled with hundreds of needle-like teeth. Fortunately they tend to be very small compared to humans.
- Research done in 2014 revealed that Stock Dinosaur Spinosaurus was likely a freshwater variant on this trope, using short, ducklike limbs to paddle its way through rivers and eating large fish out of the water with its long crocodile-like jaws. For reference, Spinosaurus itself was sixty feet long.