Translation: sea dog
Appearance: Umi inu are mysterious sea monsters found off the coast of Kōchi Prefecture in southern Shikoku. They have powerful jaws with many teeth, but their physical appearance is unknown.
Behavior: Umi inu bite into the bows or rudders of boats with their powerful jaws. They are strong enough to hold a boat in place and keep it from moving. Few fishermen have escaped their attacks and lived to tell about it.
Origin: Umi inu appear in Nanroshi, an 1815 compilation of records and essays from Tōsa Province (now Kōchi Prefecture). An encounter which took placed on the first day of the second month was recorded by harbormaster Naitō Sōzaburō.
Legends: A fisherman went out to sea one night in early spring. All of a sudden, the waves grew tall and the sea become violent. The fisherman feared his boat would capsize. Then, he heard a loud noise, as if something very large was biting into the bow of of the ship.
The fisherman hurried back to land. He felt lucky to have escaped with his life. The following day he pulled the boat up on to shore to inspect the bow. It was covered in deep teeth marks about 1.5 centimeters wide.
The fisherman showed the teeth marks to everyone he knew, but nobody could identify the creature that had made them. Finally, an elderly man from the countryside recognized the marks. He said that they were made by an umi inu—a creature which also roamed the bays further south in Hatagun, attacking fishing boats.
In Hatagun, a fisherman was returning home late one night when some creature bit into the bow of his ship and kept it from moving. The fisherman was terrified, and prayed to the gods to save him. Somehow the became able to move again, and he returned safely to shore.
The following morning he inspected his boat. Near the rudder there were six or seven deep gashes the looked like bite marks. Embedded in the grooves were two bright white, broken teeth. One was 3 centimeters long and the other was 1.5 centimeters long.