Amphibious. The crab can breathe air and water.
Claw. Melee Weapon Attack: +3 1d20+3 to hit, reach 5 ft., one target. Hit: 4 (1d6 + 1) 1d6+1 bludgeoning damage, and the target is grappled (escape DC 11). The crab has two claws, each of which can grapple only one target.