Hold Breath. The crocodile can hold its breath for 30 minutes.

Paragon. This creature has 3 HP pools, each of 75hp that can be damaged in series.

Paragon Fury.  May take one extra turn after a PCs turn for each depleted HP pool.  It also has advantage on initiative.

Reckless attack. When only one HP pool remains all attacks made and attacks made against him are at advantage.

Multiattack. Once per HP pool the crocodile makes two attacks: one with its bite and one with its tail. 

Bite. Melee Weapon Attack: +6 to hit, reach 5 ft., one target. Hit: 15 (2d10 + 5) piercing damage, and the target is grappled (escape DC 14). Until this grapple ends, the target is restrained, and the crocodile can't bite another target.

Tail. Melee Weapon Attack: +6 to hit, reach 10 ft., one target not grappled by the crocodile. Hit: 10 (1d10 + 5) bludgeoning damage. If the target is a creature, it must succeed on a DC 16 Strength saving throw or be knocked prone.

Death Roll.  When grappling and touching water, can inflict 20 (4d6+8) of piercing damage to the grapplee. 

Tail Sweep. Once per HP pool instead of making a tail attack,  can cause all creatures on the ground within 10ft to be pushed 20ft and make a DC 12 Strength saving throw or be knocked prone.

Demonic Healing. End one condition effecting the creature at a cost of 10hp.

Sink. Once per hit point pool while touching water when an attack misses him he can move up to his movement speed ans sink into the swamp, gaining cover.  He releases any grappled targets.