Pummeling Whirlpool

You draw water from the environs, swirling it into a rough torrent around you to punish your foes. Each creature in a 10-foot emanation (or 15 feet if you're in a body of water) takes 8d6 bludgeoning damage with a basic Reflex save against the higher of your class DC or spell DC. A creature that fails its save is knocked Prone. At 17th level, the damage increases to 11d6.