Azure Sea Giant Red Crab

Amphibious. The crab can breathe air and water.

Multiattack:  The crab makes one attack with its claw. If that attack hits, the crab can make one bite attack with advantage against the same target.

Claw. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 13 (2d6 + 2) bludgeoning damage, and the target is grappled (escape DC 15). The crab has two claws, each of which can grapple only one target. If the target is medium or smaller the target is restrained until this grapple ends. While grappling the target the crab has advantage on attack rolls against the target. When the crab moves any medium or smaller target it is grappling moves with it. 

Bite:  Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit:  5 (1d6+2) piercing damage.