Water Weird
Large elemental, neutral
Armor Class 13
Hit Points 58 (9d10 + 9)
Speed 0 ft., swim 60 ft.
STR
17 (+3)
DEX
16 (+3)
CON
13 (+1)
INT
11 (+0)
WIS
10 (+0)
CHA
10 (+0)
Damage Resistances fire; bludgeoning, piercing, and slashing from nonmagical attacks
Damage Immunities poison
Condition Immunities exhaustion, grappled, paralyzed, poisoned, restrained, prone, unconscious
Senses blindsight 30 ft., passive Perception 10
Languages understands Aquan but doesn't speak
Challenge 3 (700 XP)

Invisible in Water. The water weird is invisible while fully immersed in water.

Water Bound. The water weird dies if it leaves the water to which it is bound or if that water is destroyed.

ACTIONS

Constrict. Melee Weapon Attack: +5 to hit, reach 10 ft., one creature. 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 water weird. Until this grapple ends, the target is restrained, the water weird tries to drown it, and the water weird can't constrict another target.

Source : Basic Rules supplements / Creatures