Crocodopus

Amphibious. The Crocodopus can breathe air and water.

Freedom of Movement. The Crocodopus ignores difficult terrain, and magical effects can't reduce its speed or cause it to be restrained. It can spend 5 feet of movement to escape from nonmagical restraints or being grappled.

Multiattack. The Crocodopus makes two tentacle attacks, each of which it can replace with one use of Fling.

Bite. Melee Weapon Attack: +7 to hit, reach 5 ft., one target. Hit: 23 (1d8 + 2) piercing damage. 

Tentacle. Melee Weapon Attack: +7 to hit, reach 10 ft., one target. Hit: 20 (1d6 + 10) bludgeoning damage, and the target is grappled (escape DC 12). Until this grapple ends, the target is restrained. The kraken has eight tentacles, each of which can grapple one target.

Fling. One Large or smaller object held or creature grappled by the Crocodopus is thrown up to 30 feet in a random direction and knocked prone. If a thrown target strikes a solid surface, the target takes 3 (1d6) bludgeoning damage for every 10 feet it was thrown. If the target is thrown at another creature, that creature must succeed on a DC 12 Dexterity saving throw or take the same damage and be knocked prone.

The kraken can take 3 legendary actions, choosing 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.

Lightning Storm (Costs 2 Actions). The kraken uses Lightning Storm.

Ink Cloud (Costs 3 Actions). While underwater, the kraken expels an ink cloud in a 60-foot radius. The cloud spreads around corners, and that area is heavily obscured to creatures other than the kraken. Each creature other than the kraken that ends its turn there must succeed on a DC 23 Constitution saving throw, taking 16 (3d10) poison damage on a failed save, or half as much damage on a successful one. A strong current disperses the cloud, which otherwise disappears at the end of the kraken's next turn.