Oceanids are seawater nymphs who live in the Gulf of Mexico close to camp. They aren't seen very often except for when they play with the hippocampi or when they hang out with the water cabins, swimming or wrestling with them. They show up for fireworks on the beach too. They also like like playing pranks, like the time when they doused all the fireworks before the display.
The Naiads (freshwater nymphs) and the oceanids despise each other. Best thing to do is keep them at a twenty meter distance, or you'll be in for a salty-sweet waterfight! The Hermes and Ares cabin should be kept away when this occurs because then they might try and make the fight worse!