Hold Breath. While out of water, the stalker can hold its breath for 1 hour. Underwater Camouflage. The stalker has advantage on Dexterity (Stealth) checks made while underwater. Water Breathing. The stalker can breathe only underwater.
Multi-attack. The stalker can use its Enrapturing Glow if it can. It then makes two bite attacks. Bite. Melee Weapon Attack: +8 to hit, reach 5 ft., one target. Hit: 14 (2d8 + 5) piercing damage. Enrapturing Glow (Recharge 5-6). The stalker's body patterns begin to glow in an enticing manner, creating bright light in a 10-foot radius and dim light for an additional 10 feet. All creatures within 30 feet of the stalker that can see the light must succeed on a DC 14 Wisdom saving throw or move up to 20 feet directly towards the stalker. Lightning Strike (Recharge 5-6). The Monstrosity hurls a magical lightning bolt at a point it can see within 150 feet of it. Each creature within 10 feet of that point must make a DC 14 Dexterity saving throw, taking 34 (10d8) lightning damage on a failed save, or half as much damage on a successful one.
it is said when an Undertow King Stalker emerges a storm shall follow. Due to the creatures large size and innate electrical properties, it unknowingly creates a lightning storm due to the sudden change in the atmospheres electrical charge and waves as it emerges to the seas surface
wide vast deep seas, along heavy ship travel paths