Seafolk

Huge and roughly human in build, the Seafolk carried the marks of ocean life. Fins, tentacles, and gills studded their frames, and the exact mix of aquatic features shifted from one member to another.

Brutal and bent on expansion, the Seafolk saw the surface world as rightfully theirs and its inhabitants as cattle to be penned. Raw power matched that ambition. Even a solitary messenger rated Wolf-level, while ordinary warriors could heft a small truck in one hand. In numbers they rose to a Tiger-level threat, and one pack of them once drove an A-Class hero of middling rank right to the limits of what he could do.

When the Sea Monster Arc opens, the very first of them climbs out of the ocean and heads for land, only for Saitama to wipe it out before it even clears the surf. A later wave crashes onto J-City with a load of them aboard, and they haul themselves ashore to rampage through the streets. Stinger arrives and tears a trapped civilian loose from one of them. Reports afterward note that the fighting had ground the hero down to his limit, yet the invaders were still crushed, with the Deep Sea King alone left alive.

Follow-up stories track the stragglers. In one, Lord Great White, the sole holdout of the invasion, swallows the so-called King of the Lake before Saitama makes short work of him. In an OVA, a shrimp-like specimen cornered by the Blizzard Group spits Acid Spit at Lily, but Fubuki breaks up the spray and then slays it. The named members of the race are the Deep Sea King, Urn Eel, Lord Great White, and the Messenger of the Seafolk.