Ancient Crocodile

Hold Breath. The crocodile can hold its breath for up to two hours.

Poison Blood. Upon touching the skin of an Ancient Crocodile that is not at maximum HP,  creatures must make a DC 17 Constitution Save or take 4d4 poison damage. 

Multiattack. The creature makes two attacks: one with its bite and one with its tail.

Bite. Melee Weapon Attack:  +15 to hit (+20 to hit against grappled targets), reach 15 ft., one target. Hit: 69 (11d10 + 9) piercing damage, and the target is grappled (escape DC 23) if it is large or lesser. Until this grapple ends, the target is restrained, and the crocodile can't bite another target. Bite attacks against the grappled target have advantage.

Tail. Melee Weapon Attack: +15 to hit, reach 20 ft., one target not grappled by the crocodile. Hit: 44 (6d12 + 9) bludgeoning damage. If the target is a creature, it must succeed on a DC 17 Strength saving throw or be knocked prone.

Crush (Recharge 5-6). The Ancient Crocodile slams its forelegs upon the ground. All creatures in a 15-foot radius of the crocodile must make a DC 20 Dexterity saving throw, taking 71 (10d12+6) bludgeoning damage on a failed save, and half as much on a successful one. The creature may then move up to 20 feet, without provoking opportunity attacks from creatures that failed the save. 

Cha-Cha. As a bonus action, the Ancient Crocodile can rear up on its hind legs, and do the cha-cha, a type of dance. While doing so, an illusionary lei appears around its neck, and it can speak and understand Common. While speaking Common, faint tambourine music plays in the background. It can also conjure up a margarita in a salt-rimmed glass. At the end of its turn, it returns to its previous position. The illusory lei, and the margarita, disappear. The salt-rimmed glass remains, but it cannot be used to do any damage. After a period of 2d4+2 days, the glass, if upright, is filled with a random alcoholic beverage.