Hydrokinesis is the ability to manipulate and control water. This is a trait shared with water nymphs (Naiads, Oceanids, and Nereids), aquatic deities like Poseidon, Oceanus, and their offspring. Zeus also has hydrokinetic abilities, though he only controls the rain and clouds.
Hydrokinesis is a very powerful ability to have. One with the ability can create, shape and manipulate water or anything liquid-based , inorganic compound with liquid, gas (steam, water vapor), and solid (ice) states, including changing them from one state to other. This involves water itself, ice in any form, sweat, blood, steam, water pressure, poison, and other variations. With this power, a user can manipulate water-related weather such as blizzards and rainstorms. Users can also control water in all three of its physical forms and even manipulate the liquids inside another human's body to unleash gigantic tsunamis and tidal waves, users can harden water into an almost solid shape, and can use this power to walk on water, by increasing the surface tension of the water to the point where it is solid enough for other objects to stand on. Users can also create extremely durable water shields and huge solid constructs that obey thier will. It seems to be an ability possessed by the children of Poseidon, and his Roman counterpart Neptune. This ability can also be possessed by powerful children of Zeus, and his Roman counterpart, Jupiter as they are able to create strong storms that can generate rain.
- Breathe underwater for unlimited amounts of time.
- Not be harmed if they fall into the water.
- Immunity to water pressure.
- Higher resistance to fire and burns than regular people.
- Make water shoot from petrified sea shells.
- Able to create air bubbles underwater for people who cannot breathe underwater.
- Harden water to form shields or solid ground to walk on, as seen in The Demigod Files
- See in the darkness underwater.
- Naturally detect if water is fresh water or salt water.
- Make giant fists of water that mimic whatever they do to grab enemies or just smash them into the ground.
- Walk on water.
- Use water to strengthen themselves and heal most wounds and poisons
- Will themselves to stay dry in water.
- Percy, unknowingly, used hydrokinesis to pull Nancy Bobofit into a fountain.
- He used it to defend himself (again unknowingly) from Clarisse La Rue by shooting water spouts out of the toilet, when she tried to dunk his head in the toilet.
- When fighting with Ares, the god of war, Percy controlled the ocean waves to help him in the battle.
- In The Lightning Thief (film), Percy controlled the water during the battle with the Hydra to create a water wall.
- In The Lightning Thief (film), Percy controlled the water during the fight with Luke Castellan.
- In The Lightning Thief (film), Percy used high density water to make a trident.
- After Thalia Grace struck Percy with electricity, Percy angrily retaliated by summoning all the water out of the creek into an icy water typhoon to throw at her.
- Percy used it to control the sea water in fossilized shells to clean out the horses' stables at Geryon's Triple G Ranch.
- Percy used water from his own body to create a large blast of water at Mount Saint Helens. This is a very dangerous ability that left Percy very dehydrated and required him to rest for an extended period of time.
- He willed himself to stay dry when walking through a river in the Labyrinth, as well as willing himself to get wet when he is about to get picked up by the coastguard in The Lightning Thief.
- He used it to douse the fires in the battle at camp.
- He was able to still the waters so Clarisse could drive her father's chariot across the water to Manhattan.
- He controlled the waters in the River Lethe and willed himself to stay dry when submerged.
- He can make bubbles which let other people breathe underwater as seen in The Sea of Monsters and The Last Olympian. Both the times, he created water to let Annabeth breathe.
- He can walk on water.
- He can breathe under water.
- He partially used water when he created his own personal hurricane on two occasions, in The Last Olympian (against Hyperion) and in The Son of Neptune (against the legion of ghosts).
- He used it to increase the water viscosity to a level where it was almost solid. He can use it to form shields or stand on water as if it were ground.
- He can separate oxygen from water, making him able to breathe and create water bubbles when he is submerged.
- He can create huge hands made of water from the Tiber River.
- He blew up the Zhang family mansion's sprinkler system in The Son of Neptune.
- He caused a humongous wave to break the Hubbard Glacier in The Son of Neptune.
- In the war against Oceanus, Poseidon used all his power to keep the war under the sea from creating horrible disasters, like hurricanes, above the seas.
- He demonstrated an incredible amount of power over water when fighting Typhon along with the other Olympians.
- In Percy Jackson's Greek Gods, it is revealed that Zeus once brought about a global flood by causing tremendous torrents of water to pour down from the heavens all over the world for nine days and nights, with Poseidon assisting him by rapidly raising seas' water levels. As a result, the entire world was flooded (except for the highest mountains), and most of the human race was destroyed. Deucalion and Pyrrha were among the few that survived this great calamity.
- In The Crown of Ptolemy, Setne is able to generate and control a massive hurricane capable of restraining the cobra goddess Wadjet.
So far, the only major limitation of hydrokinesis is when used against certain beings (like other sea deities) who have a superior will over water and can wrest control from the weaker one. As well as being in a location where water is not abundant, or battle against a person whose ability can overcome or counteract water (e.g. Pyrokinesis). Also it appears that beings with hydrokinesis can control or create ice to a certain extent. Seen when Percy used the ice and snow around him to make an icy hurricane, as he does during the battle in Alaska in The Son of Neptune.