The Sinkhole is region in Fable II. It is a natural crevice found near the beaches of Bloodstone.
Although many seaside caves dot the Bloodstone Bay, it is in the Sinkhole that Salty Jack, a local pirate and drunk, supposedly saw the docked Marianne, the vessel of the infamous, long dead pirate Captain Dread and his crew. Because of his reputation, however, nobody pays any attention to Salty Jack. In response, he hires the Hero of Bowerstone to investigate these claims in the quest Treasure Island of Doom!
Upon cutting through some brambles surrounding the Sinkhole entrance, it is clear that Salty Jack was telling the truth, but investigation of The Marianne cannot be made until a nearby lever is pulled, raising the water level and allowing the Hero to reach the boat. After the lever is used, the cave is more or less inaccessible, as the Hero can't swim underwater; however, this makes it possible to get a silver key which was impossible to get to before.