Camouflage Lurker

Aquatic. The Camouflage Lurker can only breath underwater. 

Blood Frenzy. The Camouflage Lurker has advantage on attack rolls against a creature that is not at its hitpoint maximum.

Multiattack. The Camouflage Lurker makes three bite attacks, two claw attacks, one drag attack, and then goes invisible.  Or if it has a creature grappled it instead uses its claws.

Bite. Melee Weapon Attack. 1d20+5 to hit. 2d8+4 piercing damage, 1d8 necrotic damage, and 1d8 poison damage. If the target creature fails a DC strength 15 they are grappled in its mouth (escape DC strength 17) and while grappled the creature take 1d8 necrotic damage and 1d8 poison damage at the end of each of its turns. While having a creature grappled it cannot make another bite attack.

Drag. Melee Weapon Attack. Creatures who are grappled are pulled underwater by another 40ft or 20ft if the target beats the Camouflage Lurker in a contested strength check.

Claws. Melee Weapon Attack. 1d20+5 to hit, 3d6+5 slashing damage and 3d6 poison damage. If the target fails a DC constitution 15 they are poisoned for an hour

Invisibility. The Camouflage Lurker goes invisible and will remain invisible until a creature hits it or if it hits with all of its attacks. Once it is no longer invisible it can not go invisible for one turn and if it is critically hit it cannot go invisible for two turns.