Bo of the River

You conjure long quarterstaff of churning water in your free hand. The quarterstaff lasts for the duration of the spell. It disappears if you let go, but you can conjure the staff again as a bonus action.

You can use your action to make a melee spell attack with the quarterstaff. On a hit, the target takes 3d6 bludgeoning damage. Creatures that are immune or resistant to fire damage are vulnerable to this damage, even if they are normally resistant to bludgeoning damage (but not if they are immune).

At Higher Levels
When you cast this spell using a spell slot of 4th level or higher, the damage increases by 1d6 for every two slot levels above 2nd.