Isonade (磯撫で or いそなで, Isonade) is a creature from Japanese folklore.
Isonade are mysterious shark-like sea monsters which scour the rocky coastlines searching for boats to scuttle and fishermen to snatch. Their bodies are enormous, and their fins are covered with countless tiny metallic barbs, like a grater. They use these to hook their prey, dragging it deep into the water to be eaten. They are said to appear when the north winds blow and the sea currents change.
Despite their size, isonade are incredibly elusive. They move through the water with unparalleled grace. They can swim without creating so much as a splash, making them very difficult to notice. By the time most sailors have noticed that the winds have changed and a strange color is upon the sea, it is too late; a huge tail is already rising out of the water, above their heads. When isonade strike, they do not thrash about violently like a hungry shark, but instead hook their prey on their fins or tail with a gentle stroking motion, dragging them into the depths almost peacefully. They do this without a sound and without ever showing their bodies, making them all the more dangerous for their stealth.