The Pequod passes an island enshrouded in mist, and the night-watch hears cries that sound a lot like those of men—until the crew realizes that it’s only seals. In the night, one of the crewmembers—who happens to be the first who spotted Moby Dick, while up at the top of the main mast—falls overboard in a fit of sleepwalking. The crew throws out the life buoy to try to save him, but he does not grab onto it, and the buoy breaks away from the boat.
Once again the connection and difference between man and nature is emphasized in the familiarity of the voices of the seals. The man who falls overboard is the first member of the crew of the Pequod to die. Despite everything that has befallen the crew, they have all survived, which gives a sense that maybe the men are protected in some way. That the man who died was the first to spot Moby Dick, of course, could be taken as a bad omen.
Ahab orders that the carpenter use Queequeg’s coffin as the new life buoy, covering over its seams with “pitch” and making it water-tight. The carpenter complains that Ahab is mad and is ruining his good work, but he proceeds with the task, as ordered.
But Ahab ignores the omen, if he even notices it. The use of Queequeg's coffin as the life buoy will be significant later. It also re-emphasizes the connection between life and death that has been made throughout Moby Dick, as a coffin is now being used as a means of saving lives.