Have a read of 'Air Disaster' Vol 1. There is a detailed account of a successful ditching by a ALM DC-9 in 1970. The aircraft ran out of fuel on route to the Leeward Islands (St Croix)and ditched with 65 people on board. The aircraft (Still in one piece)sank in ten minutes even though the fuel tanks were empty.The only reason that any people were lost was through the conditions at the time.
My advise - don't run out of fuel