Just north west of the Wreck of the Brinehammer are two tiny flat islands. Face due north from the smaller (western) one and swim until a sunken chest is found.
- Skill Book (Alteration) – Sithis – Found in the sunken chest. (Only appears after the Dark Brotherhood questline is started.)
- The loot from this chest is based on the Dragonborn's level, and does not restock.
- The coordinates for the chest are X:-5563,8770 Y:129487,6875 Z:-14681,4600.