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The main courtyard was filled with warriors - mermen with fish tails from the waist down and human bodies from the waist up, except their skin was blue, which I'd never known before. Some were tending the wounded. Some were sharpening spears or swords. One passed us, swimming in a hurry. His eyes were bright green, like that stuff they put on glow-sticks, and his teeth were shark teeth. They don't show you stuff like that in The Little Mermaid.

Percy Jackson, in The Last Olympian

Merpeople are a species of mostly friendly creatures that are residents of Atlantis.

Percy Jackson and the Olympians

The Last Olympian

Percy Jackson wakes up in Poseidon's palace underneath the sea. There, he sees many merpeople wearing battle armor ready to fight the forces of Oceanus and some making underwater graves for fallen merpeople. Oceanus himself looks very much like a merman when Percy sees him on Poseidon's map of the battlefield, except he is much larger and has horns. Percy later meets his paternal immortal half-brother Triton, a merman with two fish tails instead of one, and meets his stepmother Amphitrite. During the battle, a swarm of mermen attack a large squid, but are losing the fight until Poseidon intervenes and destroys it himself.

The Heroes of Olympus

The Mark of Athena

Dozens of mermen and mermaids are seen at the underwater merpeople camp that Leo Valdez names Camp Fish-Blood. They are seen swimming through the streets, in courtyards and practicing with tridents in the area. They are trained by two ichthyocentaurs named Aphros and Bythos. Much like Camp Half-Blood, merpeople go to this camp in order to train to become effective warriors, similar to demigods. Triton himself even trained at the camp during his younger days. When Leo Valdez, Frank Zhang, and Hazel Levesque informed Aphros and Bythos about the Georgia Aquarium lead by Keto and Phorcys, they sent a group of merpeople to free them. Bill, one of the most famous and skilled of the merpeople, was chosen for the quest.


Merpeople appear human, but instead of feet they have fish-like tails. They have leathery green, blue, coral red to inky black skin color, bright green or yellow eyes like glow sticks, and shark-like teeth. Poseidon's godly son, Triton, appears to be an alternate form of a merman with two tails rather than one.


Poseidon, their ruler

Because of their underwater anatomy and exercise, merpeople can survive even in the deepest parts of the ocean.

  • Water Immunity: Their bodies allow them to survive the freezing cold temperatures at the bottom of the ocean.
  • Fighting Prowess: Much like demigods, merpeople are trained in combat as a way to survive the dangers of the ocean.
  • Swimming: Merpeople are skilled swimmers.


  • Merpeople may have a way to travel across land, as Bill was able to save the monsters in the Georgia Aquarium, despite it being in a land-locked area.
  • In Greek mythology, merpeople were called tritons, after their ancestral sea god and described as having claws, gills, shark-like skin, fangs, green seaweed-like hair, and fish tails.
  • Glaucus is another merman in Greek mythology. He was once a fisherman who ate some magical herbs that turned his hands into fins, and his legs into a tail. Later he was given the gift of prophecy and was made an oracle of the sea. He's mentioned in Percy Jackson's Greek Heroes when Jason and the Argonauts find Hercules missing.
Species: Arai | Blemmyae | Basilisks | Centaur | Cyclopes | Dragon | Drakon | Empousai | Fire-Breathing Horse | Gegeines | Gemini | Ghoul | Giant | Gorgon | Harpy | Hekatonkheire | Hippalektryon | Hippocampus | Hyperborean Giant | Ichthyocentaur | Karpoi | Katobleps | Keres | Laistrygonian Giant | Lycanthrope | Makhai | Merperson | Myrmekes | Nikai | Nymph | Pegasus | Satyr | Stymphalian Birds | Telekhine | Scythian Dracaena | Siren | Unicorns | Venti | Yales
Friendly Monsters: Argus | Blackjack | Briares | Bombilo | 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