Crab

Amphibious. The crab can breathe air and water.

Claw. _Melee Weapon Attack:_ +2 to hit, reach 5 ft., one creature. _Hit:_ 2 (1d4) bludgeoning damage, and the crab attaches to the target. While attached, the crab can't attack, and at the start of each of the crab's turns, the target takes 2 (1d4) bludgeoning damage. The attached crab moves with the target whenever the target moves, requiring none of the crab's movement. It can detach itself by spending 5 feet of its movement on its turn. A creature, including the target, can use its action to detach the crab.