Schooling
Wishiwashi becomes Schooling Form when its HP is 25% or higher.
Full effect
If this Pokémon is a Wishiwashi and level 20 or above, then when it enters battle and at the start of each turn, it becomes Schooling Form if its HP is 25% or higher and Solo Form otherwise. This ability cannot be replaced, copied, or nullified.
In game description
When it has a lot of HP, the Pokémon forms a powerful school. It stops schooling when its HP is low.
Pokemon with Schooling
Using Schooling in Cobblemon
Abilities are passive and always active, so Schooling costs you nothing to run. If it is marked hidden on a species above, expect it to be harder to obtain: servers differ in whether hidden abilities come from breeding, an Ability Patch, or events.
See the Pokedex for which abilities each species can have, and IVs, EVs and breeding for how to actually pass one down.