Above picture is just one of the various defense mechanisms used to ensure nobody can escape the Black Whale prison.

Flotsam Graveyard is a collection of various ships crashed to create a sort of barrier for the city. But, a few of these ships have been converted into a floating prison for the worst of the worst prisoners. Wizards that can easily teleport out of normal prison. Charismatic individuals who can summon entire armies. Or worst of all, someone who has angered a high enough noble that can pay off enough people to make you disappear here.

Currently, Lord Guirden is the one in control of this prison.