The Black Trench

The Black Trench was an underwater trench located in the Castillo de Jagua region of the Caribbean. The site, which was populated by numerous sharks, was explored by the pirate Edward Kenway during the early 18th century.

While searching the wreck, Edward managed to locate and loot several treasure chests that had sunk with the ship, gaining money and an upgrade plan for his own vessel, the Jackdaw.

Reference

 * Assassin's Creed IV: Black Flag