There are many secrets and optional objectives to be had in the world of “Final Fantasy VII,” in addition to a number of rare and easily missed items. One such secret area with rare items, is The Sunken Gelnika. A sunken airship sitting at the bottom of the ocean, it waits for someone to come and acquire it's hidden treasure.
In the story, on the party's quest to obtain Big Materia and keep it out of the hands of Shinra, Cloud and friends commandeer an enemy submarine, and chase after that of another enemy vessel. Upon shooting it down, the heroes obtain information leading them to other parts of the world and unable to fully explore the depths at that current time.
At this point in the game, the party gains access to the use of the stolen sub indefinitely, and therefor can go underwater and search for the sunken airship at any time until the end of the game. If the player decides to explore the vast expanses of the ocean floor, The Sunken Gelnika, a Shinra supply airship that crashed and sunk to the bottom of the sea while carrying a multitude of valuable items, can be found tucked away in a small corner of the map.
Inside, there are many precious treasures to be found. The airship is made up of four separate rooms, the Entrance, which is where the player enters at, the Research Room, branching off from the initial entrance, the Hallway, yet another branch from the entrance, and the Cargo Room, which lies at the end of the hallway. The first thing one will notice upon entrance is a glowing chest, which contains a weapon for Cloud, Heaven's Cloud.