Unlike Angel Island, the Sunken Island is located underneath the surface of Moebius's oceans, and is home to the city of Atlantinopolis, though it is still protected by a version of Knuckles as well as his associates, the Orderix. The Sunken Island was threatened with destruction when Dr. Ivo Robotnik secretly travelled to Anti Mobius and began using the Sunken Island's Anarchy Beryls to power his latest weapon. His plot was ultimately foiled however and the shield protecting the island from the water was restored. (StH: #44; :CSE)
- The Sunken Island's status following Scourge's defeat is unknown, though it was presumably liberated.