Most of the municipalities are located on the islands of the Sulu archipelago , two of them , Mapun and the turtle islands , are in the Sulu sea . Most of the municipalities are located on the islands in the Sulu Archipelago . Two of them , Mapun , and Turtle Islands lie within the Sulu Sea . Most of the municipalities are located on the islands of the Sulu sea , two of them , Mapun and the Turtle Islands , are in the Sulu archipelago .