Unusual nature. doesn't require air.

Cloaking. Creatures with a passive perception lower than 15 must make a DC 15 perception check to be able to see the creature

Multiattack. The Phalangsquido makes three attacks: one Proboscis and two Tentacle.

Proboscis. Melee Weapon Attack: +6 to hit, reach 10 ft., 1 target. Hit: 5 (1d6 + 2) [pierceing] damage and Hit: 8 (2d6 + 2) [necrotic] damage that also reduces the creatures max hit points by half the amount until they have a rest or greater restoration is cast on them.

Tentacle. Melee Weapon Attack: +6 to hit, reach 15 ft., 1 target. Hit: 8 (2d6 + 2) [bludgeoning] damage. On hit the target is grappled (escape DC 14), proboscis attacks are at advantage against a target grappled this way. Can only grapple one target per tentacle, has four.

Bonus Actions

Paralitic spray (Recharge 9-10). RangedWeapon Attack: range 15 ft cone. Hit: 8 (3d4 + 2) [poison] damage, Creatures in the area can make a constitution save DC 13, half damage on a success, on a failed save, full damage and the creature is paralyzed, the creature can repeat the saving throw at the end of each of their turns.