A small wooden barrel is used by the Warriors of Light to travel from the town of Onrac to the Sunken Shrine and back. Unlike submarines, this one is not controllable on the World Map, instead taking the Warriors of Light straight to the Sunken Shrine.
The submarine is built by Xezat Matias Surgate to allow him and the party to sneak into the Barrier Tower around Castle Exdeath. The submarine can only be used in Galuf's World. The party uses it to enter Ghido's Cave, which had been sunk by Exdeath. The submarine is yellow, perhaps as a reference to the Beatles' hit song "Yellow Submarine".
In the iOS version obtaining the submarine earns the player the achievement "Under the Sea".
Submarines are vehicles used by the Shinra Electric Power Company and are based in the Junon Underwater Reactor. The party steals one while hunting for the Huge Materia in the reactor. They can choose to fight a few Shinra Guards Cloud Strife once worked with while incognito in Junon during President Rufus Shinra's inauguration, or spare their lives.
Discovering one located in Gongaga with the help of Reeve Tuesti, the Player Turk abducts a submarine from the Junon harbor with Cait Sith and navigates the mined ocean floor to get to the village unseen.
Cid builds his submarine, Jane to allow the Comodeen to find the Flying Water required to get his airship, Sylvia, flying. However, Pist Shaz XI of Gaudium captured Jane and her occupants in the Ocean Puzzle, their adventures within taking up much of the latter half of the series.