Bake-kujira is a ghost whale or whale skeleton that haunts Japanese waters.
"Long ago, a mysterious sea creature known as the bake-kujira (lit. “ghost whale”) used to appear at night in the waters around an island in Shimane prefecture. The thing looked like the skeleton of a giant whale, and it was usually accompanied by a flock of strange birds when it came drifting in with the tide. Later, when the tide started to recede, peculiar fish would become visible in the water around the monster. Fisherman trying to catch the bake-kujira claimed their harpoons passed through the creature as if it were not there."