The Gelnika , known alternatively as the Sunken Gelnika, or Crashed Gelnika, is an optional location in Final Fantasy VII. It lies on the Bottom of the Sea to the south of Costa del Sol. The plane can only be accessed after the player has acquired the submarine from the Junon Underwater Reactor. The Gelnika holds some of the game's most difficult enemies, and also some of its best treasures. It can be visited at any time after obtaining the Shinra Sub in Part 2 or Part 3, however, if it is visited after the events of Midgar at the end of Part 2, the boss battle will not take place.