Waterbind

Choose one creature you can see within range. Purple strips of magical energy loop around the creature. The target must succeed on a Strength saving throw or be affected by the spell for its duration. In addition, a fully submerged creature affected by this spell takes 6d8 bludgeoning damage on a failure, or half as much damage on a success. While affected by this spell a creature's swimming speed (if any) is reduced to 0 feet.
If a submerged creature attempts to use it's movement to leave the water, while affected by this spell, it must make another Strength saving throw. If it fails this saving throw, it cannot leave the water this turn and takes 2d8 bludgeoning damage.
Another creature may attempt to pull the affected creature from the water by making a Strength check against your spell save DC. If this check fails the affected creature takes 2d8 bludgeoning damage.
If you maintain your concentration on this spell for the entire possible duration, and the creature has spent over half the duration fully submerged, the creature drops to 0 hit points.

At Higher Levels. If you cast this spell using a spell slot of 5th level or higher, the initial damage increases by 1d8 for each slot level above 4th.