Adult Water Elemental

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; its speed is reduced by 20 feet until the end of its next turn.

Multiattack. The elemental makes two slam attacks.

Slam. Melee Weapon Attack: +10 to hit, reach 10 ft., one target. Hit: 16 (2d10 + 6) bludgeoning damage.

Vortex (1/ Day). The elemental can conjure the elemental plane of water in its self provided it is underwater. For 1 minute the elemental's speed is doubled, it provokes no attacks of opportunity and can use the Slam attack one additional time as part of the Multiattack action.

Whelm (Recharge 4–6). Each creature in the elemental's space must make a DC 16 Strength saving throw. On a failure, a target takes 17 (2d10 + 6) bludgeoning damage. If it is Large or smaller, it is also grappled (escape DC 16). 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 Huge creature, up to two Large or up to four Medium or smaller creatures at one time. At the start of each of the elemental's turns, each target grappled by it takes 17 (2d10 + 6) bludgeoning damage. A creature within 5 feet of the elemental can pull a creature or object out of it by taking an action to make a DC 16 Strength and succeeding.