Oceanic Megafauna
The beasts of the sea, organized from most well known to least well known, are the titans of the deep from stories, myths, and ancient times.
Kraken - A kraken is a giant octopus, as simple as that. When I say giant, think big enough to entangle a boat, maybe even big enough to swallow a boat; however, that would make for some boring movie scenes. A kraken is also a challenge 23 DnD monstrosity with a strength of 30, intelligence of 22, and has the ability to summon lightning.
Megalodon - The Megalodon is a colossal shark, not unlike the great white shark, that roamed the waters 3.6 million years ago. The bite force of a megalodon could be up to about 182,000 Newtons. For reference a hippos (which are completely terrifying) have a bite force of 8,100 Newtons.
Godzillia - Godzillia is a Japanese Kaiju which means massive beast. This creature feeds on radiation, so fighting it with nuclear weapons has little effect, and will use up stored radiation to shoot out beams of energy through its mouth. Though commonly seen as a land monster, Godzillia is primarily a sea monster: it has a giant spined tail used for swimming, big legs, but small arms.
Mosasaurus - The Mosasaurus is an extinct dinosaur, swimming the seas many years before the megalodon. Most people would know what a mosasaurus looks like from watching the movie Jurassic World where in the best dinosaur scene of all time the mosasaurus eats the indominus rex at the end of the film. For those who don’t know, the mosasaurus has a jaw like a crocodile, four flippers, and a long tail.
Dragon Turtle - The name gives away this beast: Dragon Turtle, really? Not very creative. However, if you try coming up with a name for it, nothing seems to fit. Dragon turtle fits, because that is what this creature is, a dragon turtle. If you are wondering what a dragon turtle comes from, it is a DnD monster. It is a gargantuan Dragon, neutral, with strength of 25, constitution 20, and can do 15d6 fire damage in a 60-foot cone.
Ichthyosauria - Most people don’t recognize dinosaurs by their name (for example the mosasaurus) and the same goes for the Ichthyosauria. A Ichthyosauria looks like a deranged dolphin (but it's a fish not a mammal) with a long snout and fat body.
Scylla and Charybdis - These creatures are a pair of monsters in Greek mythology that some people might know from the second book in the Percy Jackson series. Scylla is a six-headed monster living in the cliffs, and Charybdis is a monster who formed a whirlpool. A traveler must choose which one to face when traveling through the Strait of Messina, though each one is dangerous. In the Odyssey, Odysseus sails closer to Scylla; he loses six men to Scylla’s heads, but would have lost his entire ship if he got close to Charybdis.
Jormungandr - At this point in this list, you might feel like the rest of these monsters are just word soup, and no one really knows of any of them. But people do know these creatures, they just might not be able to pronounce their names. Jormungandr is a giant serpent of Norse mythology said to engage in a nightly battle against Thor in Ragnarok where both of them die in the end. You would know this if you played God of War, like me, when you were only 13 years old.
Namazu - Japan is known for earthquakes. This is because Japan rests on four tectonic plates, or it could be because of the legendary catfish, Namazu. Whenever Namazu thrashes about, it causes earthquakes and tsunamis, but to prevent it from doing so, Kashima (thunder god), keeps Namazu constrained with a giant rock. But when Kashima is distracted, Namazu is left loose to cause mayhem.
Umibozu - Another legend of Japanese mythology is Umibozu. Umibozu are towering shadow spirits with white glowing eyes that were once humans drowned at sea. They quickly turn the sea into a raging storm and attempt to drown ships.
Abaia - Abaia is a massive eel from Melanesian mythology. “Another snake-like creature,” you might say. But believe me, I am sparing you. Anyways, Abaia is your perfectly large, evil sea creature. The Melanesian culture originates in islands near New Guinea and Fiji.
Hafgufa - This creature is a legendary giant sea monster of Norse mythology, so big it can be mistaken as an island. Out of all creatures in this list, the Hafgufa is the biggest. Its form is not specific: in God of War, the Hafgufa is a giant jellyfish, but in other depictions it might look more like a whale.