An Ikuchi is an extremely large sea-monster (sometimes as large as several kilometres in length) from Japanese folklore that resembled a gigantic serpent or eel.
Due to their great size they were believed to inhabit only the deepest portions of the world's oceans.
These creatures were terrifying but slow-moving predators that would secrete a sticky oil that they would use in combination with their powerful coils to capture boats and pretty much anything else they desired, constricting them until they sank and devouring any onboard.