Whale Zombie (5e Creature)
From D&D Wiki
Huge undead, neutral evil
Undead Fortitude. If damage reduces the whale to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant damage or from a critical hit. On a success, the whale drops to 1 hit point instead.
Bite. Melee Weapon Attack: +6 to hit, reaach 5 ft., one target. Hit: 21 (5d6 + 4) piercing damage.
Undead Nature. A whale zombie doesn't require air, food, drink, or sleep.