Undead Fortitude. If damage reduces the zombie to 0 hit points, it must make a Constitution saving throw with a DC of 5 + the damage taken, unless the damage is radiant or from a critical hit. On a success, the zombie drops to 1 hit point instead.

Dreadful Moan. Any creature that starts its turn within 30 feet of the zombie and can hear its moan must succeed on a DC 10 Wisdom saving throw or be frightened for 1 minute.

Clawed Hands/Bite. Melee Weapon Attack: +3 to hit, reach 5 ft., one target. Hit: 3 (1d4 + 1) slashing damage.

Decaying Slam: Melee Weapon Attack +3 to hit reach 5 ft., one target: The sea corpse zombie slams its rotting fists into a target within reach, dealing 6 (1d8 + 2) bludgeoning damage. If the target is already under the effects of the Dreadful Moan, the attack is at advantage as the sea corpse zombie's strength surges with menacing decay.

Putrid Projectile: Ranged Weapon Attack +0 to hit reach 5 ft., one target: The sea corpse zombie hurls a chunk of decaying flesh at a target within 30 feet, dealing 5 (1d6 + 2) bludgeoning damage. If the target is frightened by the sea corpse zombie's Dreadful Moan, the attack is at advantage as the putrid stench intensifies its impact.