Water fist

A fist made of water streaks toward a creature within range. Make a ranged spell attack against the target. On a hit, it takes 1d8 bludgeoning damage, and  the creature gat a -1 to his next attack or saving throw until the start of your next turn.

The spell's damage increases by 1d8 when you reach 5th level (2d8), 11th level (3d8), and 17th level (4d8).