Ghost ship

A Ghost Ship in terms of reality is a ship that is seen sailing the sea without a crew. In real life, there are cases where crews go to sea and something would happen to them (for example, they all die), leaving their ship wondering alone on the waves. Accounts of ghost ships still occur today, though usually on small vessels where the crew has perished at sea through one reason or another.

In terms of fiction, a ghost ship is a vessel that is reguarded as haunted, usually by the ghost, skeletons or zombies of her dead crew. The stereotype of a ghost ship is a vessel that seem unfit to float at sea yet despite its unsightly appearance is capable of floating on the sea as if it was not. Often they are portrayed as evil or cursed vessels and are feared by many who come across them.

One Piece
Recently the Straw Hats have come across a ship that appears to be a ghost ship carrying the Skeleton Brook.