Certain species of passive fauna in Subnautica appear to be able to swarm. The individual fish are small, indicating that they are most likely juveniles. Usually Shoals of Fish appear closer to the surface but certain species will swarm in the depths.
The fauna in a Shoal will flee from the player when approached. The player can break up a Shoal by swimming through it, but the fish will swarm again once the danger is over.
The following species can be found forming Shoals: