Water Elemental

Water Elemental CR: 5

Large elemental, neutral

Armor Class: 14 (natural armour)

Hit Points: 114 12d10+48

Speed: 30 ft , swim: 90 ft

STR

18 +4

DEX

14 +2

CON

18 +4

INT

5 -3

WIS

10 +0

CHA

8 -1

Damage Resistances: Acid, Bludgeoning, Piercing, and Slashing from nonmagical attacks

Damage Immunities: Poison

Condition Immunities: Exhaustion, Grappled, Paralyzed, Petrified, Poisoned, Prone, Restrained, Unconscious

Senses: Darkvision 60 ft, passive Perception 10

Languages: Aquan

Challenge Rating: 5

Water Form. The elemental can enter a hostile creature's space and stop there. It can move through a space as narrow as 1 inch wide without squeezing.
Freeze. If the elemental takes cold damage, it partially freezes; it's speed is reduced by 20 feet until the end of it's next turn.

Actions

Multiattack. The elemental makes two slam attacks.
Slam. Melee Weapon Attack +7 to hit, reach 5 ft, one target. Jit 13 2d8+4 bludgeoning damage.
Whelm (Recharge 5-6). Each creatures in the elemental's space must make a DC 15 Strength saving throw. On a failure, the target takes 13 2d8+4 bludgeoning damage. If it is Large or smaller, it is also grappled (escape DC 14). Until this grapple ends, the target is restrained and unable to breathe, unless it can breathe water. If the saving throw is successful, the target is pushed out of the elemental's space. The elemental can grapple one Large creature or up to two Medium or smaller creatures at one time with this ability. At the start of each of the elemental's turns each grappled target takes 13 2d8+4 bludgeoning damage. As an action, a creature within 5 feet of the elemental can pull a creature or object out of it by succeeding on a DC 14 Strength check.

Water Elementals are from the Elemental Plane of water, summoned to the Material Plane by spellcasters or other creatures. Sometimes, they make their way to the Material Plane from portal connecting both planes.