Storm Drain
Redirects single-target Water moves to this Pokémon where possible. Absorbs Water moves, raising Special Attack one stage.
Full effect
All other Pokémon's single-target Water-type moves are redirected to this Pokémon, if it is an eligible target. Other Pokémon's Water moves raise this Pokémon's Special Attack one stage, negating any other effect on it, and cannot miss it. If the move's intended target also has this ability, the move is not redirected. When multiple Pokémon with this ability are possible targets for redirection, the move is redirected to the one with the highest Speed stat, or, in the case of a tie, to a random tied Pokémon. Follow Me takes precedence over this ability.
In game description
The Pokémon draws in all Water-type moves. Instead of taking damage from them, its Sp. Atk stat is boosted.
Pokemon with Storm Drain
Using Storm Drain in Cobblemon
Abilities are passive and always active, so Storm Drain 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.