Guardian of the Fishes
The Guardian of the Fishes is a sea monster from Estonian mythology.
The Guardian of the Fishes is a hulking, monstrous, vaguely humanoid fish that can both walk on land with legs and feet and swim in the sea. In some sources it is an amphibious, fishlike giant. It has scaly humanlike hands which are used to grip prey. Its most distinguishing feature, besides its immense size, is the sawlike ridge of spines that runs down its back. The Guardian of the Fishes is the most powerful and ferocious of fishes, an ancient and gnarled, yet immensely strong creature that is impossible to catch.
As protector of all sea creatures, the Guardian of the Fishes is hostile toward humanity, especially fishermen. It creeps up on fishing boats, hidden in the murky water, and uses its strong hands to grab men from the boat and pull them under the waves. There the monster drowns them or strangles them to death.
The description of the Guardian of the Fishes resembles that of a Russian sturgeon, although this large fish (which can reach up to six feet in length and close to 250 pounds) is harmless to humans and is in fact critically endangered.