Sea Beast

Sea Beasts are a class of large aquatic mammals that inhabit the Grand Line, notable for their uncanny resemblance to surface mammals. The first Sea Beast encountered in the series is the Sea Cow Momoo.

Though somewhat similar in habitats and behavior, they should not be confused with Sea Kings, the (generally) larger and more vicious non-mammals that also inhabit the world's oceans.

Appearance
Their appearance is generally based around mammalian surface animals, such as cats, cows, elephants and many other kinds of mammals. The main difference between them and their surface counterparts are the added scales along their bodies, their fish-like fins and tail fin instead of legs and/or tails, and the ability to breath underwater through presumably gills. The majority of sea beasts are gigantic in size, easily being around the size of a kraken (which can have an estimated length of 300m (984')) and even their young can be quite huge. However smaller sea beasts, such as the Sea Squirrel exist as well which are only a bit larger than humans.

Behavior
While not as aggressively carnivorous as Sea Kings (which are, in fact, one of their natural predators), most Sea Beasts will indiscriminately attack smaller animals, including both humans and merfolk. Nevertheless, they are much easier for powerful individuals to intimidate and domesticate; according to Caribou, it is standard practice for experienced pirates to capture and harness them for underwater transportation, especially to Fish-Man Island.

In addition, at least a few types of Sea Beasts have displayed high enough intelligence and sapience to form their own underwater towns, complete with law enforcement systems.

Sea Cow


Sea Cow (海牛) is a sea creature that acts, resembles, and sounds like a normal cow; however, it is a carnivore mammal. It seems to have no problem staying on land since Arlong's crew pulled it right through Gosa Village without damaging it. Despite attacking and overturning ships, sea cows do not eat human beings. Oddly, sea cows are classified as type "A" creatures "Big Friendly". The first and so far only one that appeared is Momoo. They may be a pun on real-life dugongs and manatees, which are commonly referred to as "sea cows".

The only known sea cow has a height of 36 meters (118'1" feet) and weighs 16 tons (32,000 lbs). The fish-like scales on their bodies are actually their hardened skin, protecting their vital organs from external attacks as an armor. Besides helping them swim as fast as 70 km/h (43.5 mps), their fins contain retractable bones, sharp enough to act as claws.

Just like normal cows, sea cows have four stomachs; bacteria and parasites dwell inside them, digesting anything the cows choose to eat, including poison from venomous animals, making these creatures essentially immune to food poisoning.

Sea Cat


Sea Cats (海ネコ) are huge, cat/whale creatures that live near the shores of Arabasta. They are classified as a type "A" creature, being "Big Friendly". A huge sea cat was seen by the Straw Hat Pirates before coming to Arabasta. Vivi stated that it is a legendary animal that is a sacred to Arabasta, and must not be harmed. In the 4kids dub, she told them the "Cat Shark" was an endangered species. Their name is a pun on the Black-tailed Gull, which its name kanji is literally translated as "Sea Cat". Their appearances resemble that of a maneki-neko.

A Sea Kitten was later seen in Solo Journey of Jinbe, Knight of the Sea, where it became lost and could not find its way home. Jinbe then escorted the little sea kitten back to its underwater hometown.

Sea Boar


A Sea Boar (海イノシシ) appeared in Hatchan's cover story where Hatchan saved it from an attacking sea monster. It turns out that earlier the sea boar had eaten Camie and Pappag and spat them out shortly after being rescued.

Sea Monkey


The Sea Monkeys (シーモンキー) are sea creatures resembling monkeys. Found after returning from Skypiea and before arriving at Long Ring Long Land island, they have powerful flippers that can cause tidal waves. The Fanged Toad Pirates' ship sank due to the waves they created.

Sea Raccoon
A Sea Raccoon (海ダヌキ) differs between the anime and the manga. Both versions are visual puns on "umidanuki", the Japanese word for beaver.

In the manga, it is a giant Sea Beast, while in the anime, it is a shapeshifting animal. However, its transformations are limited to its original size, roughly that of a real raccoon, such as transforming into a doll-sized Nami. Lina is the only known person to own a sea raccoon. She and her pet, Nukky, appeared in the Spa island filler arc with her sister Sayo.

Sea Rabbit


A Sea Rabbit (海兎) is a sea creature resembling a lagomorph. One was discovered near the Red Line by Luffy, Brook, and Robin traveling in the Shark Submerge III, which consequently was defeated by a Gomu Gomu no Rifle. Upon defeat, it spits out Camie and Pappag. It share a birthday: October 19.

Sea Hippo


A Sea Hippo (海カバ) is a massive sea creature with the face of a hippo. There was a Sea Hippo among the victims of the Stomach Baron.

Sea Lion


The Sea Lion (海獅子) is a sea monster that lives in the depths of the ocean. It is 55m (180' 5") by estimate in length. One was seen in the New Fish-Man Pirates' army of sea monsters just outside Fish-Man Island, which was later ridden by the Flying Pirates during their attack at Ryugu Kingdom. After the New Fish-Man Pirates were beaten, the sea lion and its fellow sea monsters went on to cause havoc by going on a rampage. It may be based on the sea-lion, a mythical creature in heraldry with of the head and front limbs of a lion with the tail of a fish, or the merlion, another mythical creature with the head of a lion and the body of a fish. It is a visual pun on real-life "sea lions".

Sea Bear


The Sea Bear (海熊) is a sea creature that lives on the ocean floor. It is 50m (164') by estimate in length. The only one seen is under the command of the New Fish-Man Pirates, and it appeared first alongside the Sea Lion and many other sea beasts under the crew's command. It was on a rampage, but stopped when some fish-men tried to frighten it with fire. The kanji for sea bear can mean "fur seal" in Chinese, which the sea bear somewhat resembles.

Sea Giraffe


The Sea Giraffe (海キリン) is a large sea beast resembling a giraffe that lives deep in the ocean floor. One was under the ownership of the New Fish-Man Pirates where it served as Hammond's steed and usually traveled and fought alongside its fellow sea beasts. It was used during the New Fish-Man Pirates' invasion of Fish-Man Island. After the defeat of the New Fish-Man Pirates, the sea beasts went on a rampage and destroyed everything in their way.

Sea Elephant


The Sea Elephant (海ゾウ) is a massive aquatic pachyderm that lives in the depths of the sea. One sea elephant was one of the many sea monsters under the control of the New Fish-Man Pirates. The sea elephant and its fellow sea beasts were used during the New Fish-Man Pirates' attack on Fish-Man Island. After the New Fish-Man Pirates were defeated and arrested, the sea elephant and its fellow sea beasts went on a spree of destruction. The sea elephant is a visual pun on real-life "sea elephants".

Sea Rhinoceros


The Sea Rhinoceros (海サイ) is a sea beast that lives deep in the sea. A sea rhinoceros was seen among the New Fish-Man Pirates' army of sea monsters just outside Fish-Man Island, and were later ridden by the Flying Pirates during their attack on Ryugu Kingdom. After the New Fish-Man Pirates were subdued, the sea rhino and its fellow sea beasts went on a rampage of destruction.

Sea Gorilla


The Sea Gorilla (海ゴリラ) is a sea monster resembling a gorilla that lives in the depths of the ocean. One was seen as part of the New Fish-Man Pirates' army of sea beasts just outside Fish-Man Island, and were later used by the Flying Pirates during their attack on Ryugu Kingdom. After the fall of the New Fish-Man Pirates, the Sea Gorilla and a few of the sea beasts went on a spree of destruction.

Sea Squirrel


A Sea Squirrel is smaller species of sea beast. One was under the ownership of the New Fish-Man Pirates. It was used by Hammond to attack Luffy, but the beast was easily subdued by Luffy's Haoshoku Haki.

Sea Leopard


A Sea Leopard was one of New Fish-Man Pirates' sea monsters. After beginning their conquest of Fish-Man Island, the New Fish-Man Pirates released it along with their other Sea Beasts to aid them in battle.

Sea Pig
Sea Pig (海ブタ) is an ingredient for one of the Attack Cuisine dishes, Hormone Soup with Sea Pork. The name is a pun on the Japanese word for dolphin (海豚), the kanji of which literally translates to "sea pig".

Sea Dog


Sea Dog (海イヌ) is a Sea Beast resembling a dog. In Solo Journey of Jinbe, Knight of the Sea, one is seen working as a police officer, wearing a police hat and badge, and even having a mustache.

Translation and Dub Issues
The Viz manga initially translated Momoo's class as the more generic "sea monster", with the term "Sea Beast" not being until its translation of Volume 17's SBS (which confirmed that Momoo and creatures like him belonged to a category distinct from Sea Kings). Interestingly, the original Japanese term, Kaijū (海獣), is used in real life for ordinary marine mammals such as dolphins and whales; it remains unknown whether those of One Piece (e.g. Laboon) are also categorized as such.

(As an aside, it should be noted that this Kaijū is not the Kaijū (怪獣) used to describe Godzilla and other classic Japanese film monsters, though the two are homonymous.)