AC 15 (natural armor)
HP 9 (2d8; bloodied 4)
Speed 30 ft., swim 30 ft.
Proficiency +2; Maneuver DC 12
Skills Stealth +4
Senses blindsight 30 ft., passive Perception 9
Amphibious. The crab can breathe air and water.
Claw. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 4 (1d6+1) bludgeoning damage and the target is (escape DC 11). The crab has two claws and can grapple one creature with each.
Beasts are natural animals whose existence and abilities are nonmagical. Aand a are both beasts.