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Sea Kings are huge, carnivorous monsters that inhabit all of the world's oceans.[1] They are especially prevalent throughout the Calm Belts surrounding the Grand Line, and as such are one of the most common—and notorious—hazards encountered by seafarers in the area.[4]

Though somewhat similar in habitats and behavior, they should not be confused with Sea Beasts, the (generally) smaller and more docile mammals that also inhabit the world's oceans.[5]



Sea Kings vary radically in physical build, to the point that no two individuals have been observed with matching physiques, proportions, or even colorations. How many—if any—of these are distinct species remains unknown.

The feature most "common" to Sea Kings in general is a long, vaguely serpentine body, though this is by no means universal. One particular specimen encountered by the Straw Hat Pirates was even noted to look like an oversized frog, complete with distinct toes instead of fins or flippers.[6]

Apart from this, Sea Kings are mostly defined by their size. The smallest known specimen, Dawn Island's "Lord of the Coast", can comfortably swallow a grown man (and most of a dinghy) whole; larger specimens are known to easily dwarf whole cities and even islands.

Lord of the Coast Anime Infobox.png
The Lord of the Coast, a relatively small Sea King.
Master of the Waters Manga Infobox.png
The Master of the Waters was bigger than many large ships.
Little Garden Infobox.png
The largest structures on Little Garden are the skulls of two Sea Kings slain by Dorry and Brogy over a century ago.


They are classified as Type "C" creatures, "Big Savage".[7] This is largely justified by their near-constant preying on other creatures, even comparatively tiny humans; once a Sea King has zeroed in on prey, it will attack relentlessly, and only retreat in the face of overwhelming physical (more rarely, mental) force.

However, they are not entirely mindless predators, as proven by their mental link through Poseidon. Though incapable of physical speech, they can deliver wholly coherent thoughts through telepathy—chief among them a genuine reverence toward whichever mermaid currently holds the Poseidon bloodline. In addition, while they feel no special kinship toward humans as a whole, they are entirely capable of acknowledging, and even respecting, an individual human's strength.

Abilities and Powers

Sea Kings make trade and travel difficult for anyone trying to cross the water where they are found as they are exceptionally fierce and strong compared to many other sea creatures. They are powerful predators and attack unprovoked with no fear or signs of backing down, with the only exceptions being the cases where they themselves were the hunted. Cases have arisen where some islands in the Grand Line close to the edge of the Calm Belt (their natural breeding ground) have ended up getting almost completely cut off from the rest of the world due to the Sea Kings themselves.

Most other creatures in the ocean fear the Sea King, with some notable exceptions:

  • Bananawani: their only natural predator.
  • Yuda: who are too ferocious even for them and also poisonous.
  • Blue Gorillas: Impel Down guards who are extremely good swimmers and incredibly strong, cutting Sea Kings up for food.
  • Giants: who are incredibly strong themselves.

Only the strongest of ships or captains can take on a Sea King. Confrontation with one by a few humans is inadvisable and is considered nothing short of suicide. The fish-man Jinbe also acknowledged the danger Sea Kings posed after summoning whale sharks into the Calm Belt, thus proving at the very least fish-men are also aware of their potential threat. Many people, such as Franky, see the act of killing one a sign of strength and achievement.

Their perception, however, can be easily fooled by Seastone. When something is covered in Seastone, they will not notice the object at all, as they'll mistake it for the ocean. The marines use that for their advantage and cover their ships with Seastone to avoid being attacked by Sea Kings. Vice Admiral Momonga implied that Sea Kings cannot be fooled for very long, though, and that they'll eventually notice the ship anyway.


Even though the Mermaids can communicate with fish in the sea, the Sea Kings are beyond their reach. This indicates that they are very different to the other aquatic inhabitants of the ocean. Ryuboshi once commented that he always dreamt of riding on the back of a Sea King. However, according to legend, once every few centuries a mermaid is born with the ability to speak to the Sea Kings; on that day the world will change forever, then one day a man will appear to guide that mermaid. The name of the previous Mermaid turned out to be Poseidon, whose abilities were considered a weapon that is able to destroy the world and whose power is in line with the other two ancient weapons called Pluton and Uranus. This power implies that the Sea Kings are very powerful indeed, but it is noted that due to the nature of this ability, when used for the greater evil, it is a most dangerous ability, as if they are drawn into a rage by the Mermaid's ability unintentionally through shock due to the mermaid's lack of control, they can destroy and sink every land mass into the ocean.

In the past, Vander Decken went looking for a mermaid princess of legend with this ability and was drawn to the bottom of the ocean in his search. The search continued with every member of his family thereafter until Vander Decken IX. Shirahoshi is the current mermaid with this ability.[8]

Besides the mermaid of legend, the only other people who seem to be able to hear the Sea Kings have been Monkey D. Luffy, Kozuki Oden, and Gol D. Roger. The latter was said to be able to "hear the voice of all things".


The Distant Past

800 years ago during the Void Century the Sea Kings made a promise to tow the ship Noah thanks to the mermaid known as Poseidon's and her abilities. However, Joy Boy, who made the deal with Fish-Man Island and Poseidon, failed to keep up his end of the bargain and Noah was never used leaving its mission unknown.

The Sea King Menace

Sea Kings occupy the Calm Belt. In the past their reputation and numbers have been the sole protection for Amazon Lily located inside the Calm Belt itself. However elsewhere, islands close to it such as Water 7 remained cut off.

Instances Throughout History

Sea Kings summoned by Shirahoshi.

  • During Mont Blanc Noland's return to Jaya, the two ships led by his king encountered a Sea King themselves. Terrified of such a beast, the king left Noland to handle it by himself. In a published false story, however, the king himself was the hero who defeated the Sea King.
  • Sea Kings were the reason behind Dorry's and Brogy's contest to see who was the stronger warrior. They caught one each and began arguing over who caught the bigger Sea King.
  • Yorki is believed to have perished when he attempted to flee the Grand Line via the Calm Belt.
  • Franky began his attempt to beat one of these beasts as a child. He began building the Battle Frankys. Ten years before the storyline, he successfully kills a Sea King. However, his ships for killing Sea Kings would later become part of a plan hatched by Spandam.
  • Twelve years ago, Higuma is killed by a Sea King and Shanks loses an arm to the same Sea King while saving the life of Monkey D. Luffy.
  • Ten years ago, it is revealed that Shirahoshi has the ability to control Sea Kings, while unknowingly using this ability to save her mother.

Changing Times

After centuries of ruling the sea, the Sea Kings' control over the Calm Belt has been lessened. Dr. Vegapunk discovered that Seastone emits the same aura as the sea, resulting in the Marines lining the hulls of all their ships with it and thus are completely ignored by the Sea Kings. For the first time, ships can move in and out of the Grand Line freely. Also, the Sea Train was invented by Tom to create trade and travel between Water 7 and its neighboring islands, and was designed to create a noise that repels Sea Kings.

Fish-Man Island

Sea Kings moving Noah.

During the Fish-Man Island Arc, the Sea Kings were summoned by Shirahoshi's will to become Luffy's strength. The Sea Kings lend their strength to aid Luffy in protecting the island by stopping Noah from crashing into the island.[9] In the process, they also protected the ship from being completely destroyed by Luffy. They then reveal to Shirahoshi that it was indeed her that called them and it was her wish to aid Luffy that led to their actions. The Sea Kings go on saying that Shirahoshi has been destined to be their queen and they move Noah to the Sea Forest where it will be fixed.[10]

Translation and Dub Issues

Most professional English translations do not render the kanji 海王 literally—that is, as Sea King. Instead, they favor the more metaphorical translation Neptunian, referencing Neptune, the Roman God of the sea. This translation was likely inspired by the Japanese term for the planet Neptune (海王星 Kaiōsei?, lit. "Sea King Star"), itself an homage to the Western astronomers who had discovered it.

(Note that the "Neptunian" translation predates the Fish-Man Island Arc by roughly half a decade. The significance that the term Neptune—and for that matter, Poseidon—would later have in the series is completely incidental.)

Funimation Entertainment's "uncut" anime dub uniquely averts this convention and refers to the creatures as Sea Kings, though Neptunian is still used in both its edited-for-TV dub and its simulcast subtitles. In contrast, the 4Kids-dubbed anime removes the creatures almost entirely (as their largest roles in the early storyline were during the Reverse Mountain Arc and the Little Garden Arc, both truncated), and offers no specific term whatsoever.


One of the unnamed Sea Kings that is regularly reused within One Piece.

  • Very few Sea Kings have "official" names; only those who commonly inhabit the same waters receive any names at all. The Sea King that ate Shanks' arm is known as Lord of the Coast, and Long Ring Long Land island had a Sea King called Master of the Waters.
  • Sea King meat is apparently considered a delicacy as Luffy has claimed that food made out of Sea King meat is "very good stuff".[11] It is also one of Zoro's favorite foods.
  • Though nameless, some of the Sea Kings seen early in the series often crop up in intros and outros even though Oda himself has never reused them for the storyline until Chapter 647 in which many anime-familiar sea kings appear all at once in the same panel. Notably, a puffy white Sea King with a bird's beak has been in multiple introductions.
  • Sea Kings and the other large sized monsters of the world are most likely based on the illustrations of Sea monsters found on old maps, often placed on the map as a warning to sailors traveling in those waters as a result of local superstitions. This practice was abandoned with the use of modern cartography techniques.
  • The Sea Kings that Shirahoshi inadvertently summoned to stop the Noah from falling were the exact same group of Sea Kings that were first shown when the crew unintentionally entered the Calm Belt, and were assumed to be hostile at the time.


  1. 1.0 1.1 One Piece Manga and Anime — Vol. 1 Chapter 1 and Episode 4, The series' first Sea King, the Lord of the Coast, emerges outside the Grand Line.
  2. One Piece Manga and Anime — Vol. 11 Chapter 92 and Episode 42, Sanji likens the enraged Arlong's eyes to those of a Sea King; an image of the Lord of the Coast is offered as a point of comparison.
  3. One Piece Blue Deep: Characters World (p. 13), Their estimated size is revealed.
  4. One Piece Manga and Anime — Vol. 12 Chapter 101 (p. 8-9) and Episode 55, Accidentally sailing into the Calm Belt, the Straw Hat Pirates almost instantly run into a massive nest of Sea Kings. The anime makes this scene part of the Warship Island Arc, placing Apis amongst the Straw Hats.
  5. SBS One Piece Manga — Vol. 17 (p. 66), Oda explains that Sea Kings are a distinct class from Sea Beasts such as Momoo.
  6. One Piece Manga and Anime — Vol. 12 Chapter 101 (p. 11) and Episode 55, The giant-frog Sea King tries to eat Usopp, who is narrowly saved by Luffy. In the anime, its would-be victim is changed to Apis.
  7. One Piece Blue: Grand Data File, Classification of Sea Kings.
  8. One Piece Manga and Anime — Vol. 63 Chapter 625 and Episode 545, Vander Decken IX speaks of what the Mermaid Princess is capable of, and how Shirahoshi has inherited the gift.
  9. One Piece Manga and Anime — Vol. 66 Chapter 647 and Episode 567, the Sea Kings response to Shirahoshi's call and stop Noah.
  10. One Piece Manga and Anime — Vol. 66 Chapter 648 and Episode 568, the Sea Kings move Noah to the Sea Forest.
  11. One Piece Manga and Anime — Vol. 54 Chapter 524 and Episode 419, Luffy eating Sea King ham.

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