Limited Amphibiousness.

The sea spawn can breathe air and water, but it needs to be submerged in the sea at least once a day for 1 minute to avoid suffocating.

Multiattack.

The sea spawn makes two Unarmed Strike attacks and one Piscine Anatomy attack.

Unarmed Strike.

Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) bludgeoning damage.

Piscine Anatomy.

The sea spawn uses one of the following options (choose one or roll a d6):

1–2: Bite. Melee Weapon Attack: +4 to hit, reach 5 ft., one target. Hit: 4 (1d4 + 2) piercing damage.
3–4: Poison Quills. Melee Weapon Attack: +4 to hit, reach 5 ft., one creature. Hit: 3 (1d6) poison damage, and the target must succeed on a DC 12 Constitution saving throw or be poisoned for 1 minute. The target can repeat the saving throw at the end of each of its turns, ending the effect on itself on a success.
5–6: Tentacle. Melee Weapon Attack: +4 to hit, reach 10 ft., one target. Hit: 5 (1d6 + 2) bludgeoning damage, and the target is grappled (escape DC 12) if it is a Medium or smaller creature. Until this grapple ends, the sea spawn can't use this tentacle on another target.

Environment: Coastal, Underwater

Sea Spawn