Ishmael explains why they tied the whale to the ship and left it there overnight: because slaughtering a whale is such an arduous process, when a whale is captured late at night, it’s standard procedure to tie it to the ship overnight and let everyone get a good night’s sleep before they start the butchering process.
Sometimes, however, especially near the equator in the Pacific, there are too many sharks for this— they can strip a whale bare in a few hours.
In the morning, to get rid of the sharks, Queequeg and another seaman are lowered over the side of the Pequod on platforms, holding their whaling-spades, to kill as many sharks as possible in a vicious bloodbath.
They haul one of the sharks in over the side of the ship to get its skin, and, not quite dead, it almost bites Queequeg’s hand off. Queequeg responds with a racial slur.