Bilgewater Kraken

Siege Monster: The Kraken deals double damage to objects and structures.

Magic Resistance: The Kraken has advantage on saving throws against spells and other magical effects.

Amphibious: The Kraken can breathe both air and water.

Multiattack: The Kraken makes three tentacle attacks, each of which it can replace with one use of Fling.

Tentacle: Melee Weapon Attack: +17 to hit, reach 30 ft., one target. Hit: 20 (3d6 + 10) bludgeoning damage. If the target is a creature, it is grappled (escape DC 20). Until this grapple ends, the target is restrained. The Kraken has ten tentacles, each of which can grapple one target.

Fling: One Large or smaller object held or creature grappled by the Kraken is thrown up to 60 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) blurring damage for every 10 feet it was thrown. If the target was thrown at another creature, that creature must succeed on a DC 18 Dexterity saving throw or take the same damage and be knocked prone.

Bite: Melee Weapon Attack: +17 to hit, reach 5 ft., one target. Hit: 23 (3d8 + 10) piercing damage.

Ripple Counter: When a creature hits the Kraken with a melee attack while within reach of its tentacles, the Kraken can use its reaction to make a tentacle attack against that creature.

The Kraken can take 3 legendary actions, selecting from the options below. Only one legendary action option can be used at a time and only at the end of another creature's turn. The Kraken regains spent legendary actions at the start of its turn.

Tentacle Attack or Fling: The Kraken makes one tentacle attack or uses its Fling action.

Grasping Tentacles (Costs 2 Actions): The Kraken uses its tentacles to create a dangerous terrain in a 20-foot radius centered on itself. The area becomes difficult terrain for non-Kraken creatures until the start of the Kraken’s next turn. In addition, each creature of the Kraken's choice in that area must succeed on a DC 20 Strength or Dexterity saving throw (target's choice) or be restrained until the terrain disappears. A creature can use its action to attempt a DC 20 Strength or Acrobatics check to free itself or another creature within its reach, ending the effect on a success.

Capsize (Costs 3 Actions): The Kraken targets one vessel of Huge size or smaller within 60 feet of it. The vessel must make a DC 20 Constitution saving throw against this magic or capsize. All creatures on the vessel must also make a DC 15 Dexterity saving throw or fall overboard, landing prone in the water in the vessel's space. The Kraken can target larger vessels by spending additional legendary actions for each size category above Huge.