Storm Drain is an ability introduced in generation 4.
8 Pokémon can have this ability, such as Shellos, Gastrodon, Finneon, Lumineon and Lileep. For 4 of them it is the hidden ability, usually obtained from events, raids or breeding.
Official effect
Redirects single-target Water moves to this Pokémon where possible. Absorbs Water moves, raising Special Attack one stage.