A sea serpent is a type of a sea monster either wholly or partly serpentine. They resemble to Drakons and Dragons, but do not spit poison, live in water, and hold other minor differences. Poseidon has the ability to control the sea serpents/monsters.

Percy Jackson and the Olympians

The Sea of Monsters

Percy Jackson notices that sea serpents prefer to live in the Sea of Monsters.

The Battle of the Labyrinth

When Percy arrives at camp he starts walking around and sees a group of half-bloods on a Greek trireme fighting a large orange sea serpent on the canoe lake. He calls it a typical day at camp.

The Demigod Files

The Stolen Chariot

A sea serpent with a head like a crocodile was used by Deimos to scare people and attack his demigod sister, Clarisse La Rue, and Percy. It is said by Percy that they are "big babies when it comes to getting hurt".

The Last Olympian

Oceanus used a sea serpent as a sword when he attacked Poseidon's palace. One sea monster tried to attack the palace but Poseidon blasted it with his trident. After the Second Olympian War, while fishing, Poseidon talks to Percy and catches a huge green sea monster but cuts it loose saying it was "not eating size".

The Heroes of Olympus

The Lost Hero

Aeolus says that Jason came to him seeking the location of the Trojan Sea Monster.

The Son of Neptune

It is mentioned that Percy strangled a sea monster in the Carquinez Strait.

The Mark of Athena

One of Keto's children, a skolopendra attacks the Argo II and damages the ship. It tries to capture Frank Zhang, Leo Valdez, and Hazel Levesque but Leo and Hazel throw Greek fire into its mouth and it drops them. They are then rescued by Ichthyocentaurs, who remark that Keto must really hate the demigods since she sent one of her biggest monsters after them.

Notable Sea Monsters


  • Sea Monsters were often used on maps to mark areas of the sea that had not yet been explored.
Species: Arai | Blemmyae | Basilisks | Centaur | Cyclopes | Dragon | Drakon | Empousai | Fire-Breathing Horse | Gegeines | Gemini | Ghoul | Giants | Gorgons | Harpies | Hekatonkheires | Hippalektryons | Hippocampi | Hyperborean Giants | Ichthyocentaur | Karpoi | Katoblepones | Keres | Laistrygonian Giants | Lycanthrope | Makhai | Merpeople | Myrmekes | Nikai | Nymphs | Pegasus | Satyrs | Stymphalian Birds | Telekhines | Scythian Dracanae | Sirens | Unicorns | Venti | Yales
Friendly Monsters: Argus | Blackjack | Briares | Chiron | Cottus | Don | Ella | Festus | Gleeson Hedge | Gray | Grover Underwood | Guido | Gyges | Lysas | Mellie | Mrs. O'Leary | Ophiotaurus | Peaches | Peleus | Porkpie | Rainbow | Scipio | Tyson | Tempest | Sssssarah
Enemy Monsters: Antaeus | Agrius and Oreius | Arachne | Cacus | Carthaginian Serpent | Charybdis and Scylla | Chimera | Chrysaor | Clazmonian Sow | Colchis Bulls | Echidna | Euryale | Geryon | Joe Bob | Kampê | Kekrops | Ladon | Lamia | Manticore | Medusa | Minotaur | Nanette | Nemean Lion | Polyphemus | Python | Sphinx | Stheno | Typhon | Trojan Sea Monster
Neutral Monsters: Carnivorous Sheep | Cerberus | Erymanthian Boar | Gray Sisters | Flesh-Eating Horse | Furies | Gryphon | Orthus | Skolopendra | Sybaris