Octopus

Hold Breath. While out of water, the octopus can hold its breath for 30 minutes.

Underwater Camouflage. The octopus's Stealth is 18 while underwater.

Water Breathing. The octopus can breathe only underwater.

Tentacles. _Melee Weapon Attack:_ +3 to hit, reach 5 ft., one target. _Hit:_ 3 (1d4+1) bludgeoning damage, and the target is grappled (escape DC 11), if it is a Medium or smaller creature. Until this grapple ends, the octopus can't use its Tentacles on another target.

Ink Dash (Recharge 6). When a creature the octopus can see deals damage to it, the octopus can release a 5-foot-radius cloud of ink all around itself, if it is underwater. The area is heavily obscured until the end of the octopus's next turn, although a significant current can disperse the ink. Then, the octopus can swim up to its swimming speed. If it does so, it immediately releases any creature it is grappling.