Multiattack

Two Desiccating Slam attacks.

Desiccating Slam

Melee Weapon Attack: +6 to hit, 5 ft., one creature,. 12 (2d8+3) bludgeoning damage + 7 (2d6) necrotic. Target's hp max reduced by amount equal to necrotic taken (DC 15 Con negates hp max). Reduction lasts until target finishes long rest. Target dies if effect reduces its hp max to 0.

Wave of Seawater (Recharge 5-6)

Throws its hand forward sending wave of seawater in a 30' cone. Each creature in that area: 21 (6d6) bludgeoning damage and begins choking as its lungs fill with seawater (DC 15 Dex half damage and isn't choking). A creature that can breathe water doesn't choke from failing this save. A choking creature can make a DC 15 Con save at the end of each of its turns coughing up seawater and success ends effect on itself.