Sunken treasure

Sunken treasure is a chest that can be gathered from the bottom of the ocean by using the Grappling Hook while on the boat over the sea. Sunken treasure can be found by salvaging over light rings that appear in the sea when their corresponding Treasure Chart has been opened or when their corresponding Triforce Chart has been both opened and deciphered by Tingle. Light rings will also appear when defeating Big Octos and certain Gunboats. There are also light rings that appear in the overworld without any charts or enemies--with some only appearing at night--but these will not be randomized on any settings and will only contain Rupees.