How do you get a sunken ship to the top again?

More than one technique has been used, to raise sunken ships. You can position another ship above the sunken ship and then simply attach a cable (or several cables) and winch it up. You can also attach large balloons to the ship and then inflate them from cans of compressed gas, and float the ship up. Sometimes divers remove pieces of a ship and carry the pieces away by hand; the ship can be reassembled (if that's what they want to do) from the pieces, in a ship yard.