Like smugglers, rumrunners are notorious for delivering contraband throughout the Caribbean. The only difference is that instead of delivering illegal spices and other goods, rumrunners naturally only deal with rum. These unknown fiends apprently worked off a base island known as Rumrunner's Isle. Here they kept a secret cache were they could hide their provisons such as food, water and rum. It was on this island were the rumrunners met Jack Sparrow, after he was marooned. After Jack's barterings, the rumrunners agreed to take him aboard their ship.
On Jack's second return to Rumrunner's Island, it is revealed that the rummrunners were out of buisness, presumably caught and hanged by Norrington and the East India Trading Company.