What object keeps Ishmael afloat after the Pequod sinks?

Queequeg's coffin keeps Ishmael afloat after the Pequod sinks. The coffin was originally built for Queequeg when he fell gravely ill and expected to die during the voyage.

When a sailor later falls overboard and the ship's life buoy is lost, Queequeg's coffin is waterproofed and converted into a replacement buoy. During the final chase, Moby-Dick destroys the Pequod and leaves Ishmael alone in the sea. The coffin rises from the ship's vortex, allowing him to cling to it for a day and a night.

The detail is more than a practical rescue device: it links Queequeg's expected death with Ishmael's survival. Ishmael is the only member of the Pequod's crew to survive, and the Rachel eventually finds him while searching for its own missing sailors. A common mix-up is to call the object a raft or ordinary life buoy; it is specifically Queequeg's coffin, repurposed as a life-saving float.