Invisible in Water. The big water slurpent is invisible while fully immersed in water.
Water Bound. The big water slurpent dies if it leaves the water to which it is bound or if that water is destroyed.
Constrict. Melee Weapon Attack: +5 to hit, one target. Hit:13 (3d6+3) bludgeoning damage. If the target is Medium or smaller, it is grappled (escape DC 13) and pulled 5 feet toward the big water slurpent. Until this grapple ends, the target is restrained, the big water slurpent tries to drown it, and the big water slurpent can't constrict another target.
The Big Water Slurpent is a magical creature that has lived within the Big Water for centuries. It was created by a wizard to guard the tower that has long since sunk into the Big Water. Many goblins have seen the slurpent and have run away. Many goblins believe that it likes to eat goblins.