Characters: Female Rhydon and Male Samurott (Nintendo's Pokemon)
Screenshot taken from Valve's Garry's Mod.

Daddy Samurott has been one of good friends with Big Mama Rhydon and they sometimes have fun underwater and bloat their bellies up huge by storing up their Hydro Pump and/or Water Pulse, that way, in order to swim easily, they would BE the water, lol!