Squirtle Drowning.
Swimming is a mechanic introduced in Super Smash Bros. Brawl. Characters can swim in areas with water, like the Pirate Ship, and some levels of the Subspace Emissary. If characters swim for too long, they can drown. When a character begins to drown, it seems like they are splashing about, but with a frown on their faces. In the Subspace Emissary, any enemy that happens to touch the water will be instantly K.O.'d. The time the characters stay afloat before drowning differs on how much damage they have.