Dungeons and Dragons 5th Edition Monster Manual pg 320
Crab
Tiny beast,
Armor Class: 11
Hit Points: 2 (1D4)
Speed:
20 ft
, swim: 20 ft
Skills: Stealth +2
Senses: Blindsight 30 ft
Challenge Rating: 0
Amphibious. The Crab can breathe air and water.
Actions
Claw. Melee Weapon Attack: +0 to hit, reach 5 ft., one target. Hit: 1 Bludgeoning Damage.
Crabs are generally covered with a thick exoskeleton, composed primarily of highly mineralized chitin and armed with a pair of claws. Crabs vary in size from a few millimeters wide to a leg span of 13 feet.