Acid Immunity. The snake is immune to acid damage (not caused by it's water sensitivity trait) and has advantage on saving throws against poison - it always succeeds on saving throws against acid related effects (not caused by it's trait).

Water Sensitivity. For every 5 feet the snake moves in water, or for every gallon of water splashed on it, it takes 1 acid damage: it has disadvantage on saving throws against water based spells and attacks.

Bite. Melee Weapon Attack: +6 to hit, reach 15 ft., one target. Hit: 11 (1d12 + 4) piercing damage, and the target must make a DC 15 Constitution saving throw, taking 5 (1d10) poison plus 5 (1d10) acid damage on a failed save, or half as much damage on a successful one.

Constrict. Melee Weapon Attack: +6 to hit, reach 5 ft., one creature. Hit: 17 (3d8 + 4) bludgeoning damage, and the target is grappled (escape DC 16). Until this grapple ends, the creature is restrained, and the snake can't constrict another target.