Sailors used to face severe punishments if they behaved badly.
Keel-hauling was a fairly common form of punishment for severe crimes on board ship during the 16th and 17th centuries. A rope was passed from one end of the main yard (the spar that ran across the mast holding up the square mainsail) then below the ship and up to the other end of the main yard . The victim was tied to the rope, with weights fixed to his body, and dragged to and fro beneath the ship from one side to the other. A gun was often fired while he was under the water, to frighten him still more, and his body would get torn and bruised by the marine growth on the hull of the vessel. At the beginning of the 18th century, keel-hauling was replaced by the cat o'nine tails, a knotted rope with nine ends, with which the victim was whipped.