Anomalocaris

This creature can breathe underwater freely, but can only breathe air with damp gills. (moist air or 1 gallon of water per hour)

Carapace. All incoming damage is reduced by 5 before applying weakness or resistance. This ability does not affect cold or psychic damage.

Multiattack. This creature can use four attacks, or a spell and a tail smash.

Spellcasting. The Aspidochelon is a 5-level spellcaster. Its spellcasting ability is 20 (spell save DC 15, +5 to hit with spell attacks). The Aspidochelon has following spells prepared:
Cantrips (at will): Frostbite, Poison Spray
1st level (9 slots): Color Spray, False Life

These spells do not count as magical and do not count as actual spells. Rather, this creature has natural abilities very similar to the spells.

Slickening. The Aspidochelon gives a creature within touching distance a +5 to their AC for the next 2 turns. (Cooldown:8 turns) 

Claw. Melee Weapon Attack: +10 to hit, reach 5 ft., 1 target. Hit: 15 (2d10 + 4) slash/pierce damage. (creature chooses damage type) 

Tail Smash. Melee Weapon Attack: +7 to hit, range #5 ft., 1 target. Hit:  20 (3d10 + 4) bludgeoning damage. (Cooldown:1 turn)

Spherical Eye Stalk . Aspidochelon cannot be flanked or gain disadvantage on perception checks .