Submarine ( Final Fantasy VII ) Submarines are underwater vehicles used by the Shinra Electric Power Company in the " Compilation of Final Fantasy VII " . They are primarily used around Junon and to explore the area around the Junon Underwater Reactor . Submarines are the only vehicles in " Final Fantasy VII " that can submerge below the ocean floor and explore the Bottom of the Sea locations . They can be docked and picked up at various natural harbors next to Junon , near the Gold Saucer , and just outside Lucrecia ' s Cave . Story . " Before Crisis - Final Fantasy VII - " . Considered fugitives by the Shinra management due to their involvement and collaboration with Veld , the Turks attempt to locate the required support materia needed to help Veld ' s daughter , Elfé . 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 . " Final Fantasy VII " . The party steals a " Shinra Sub " while hunting for the Huge Materia in the underwater reactor . While boarding the vessel , they can choose to fight a few Shinra guards , the same three guards Cloud meets when he after he first jumped into the higher levels of Junon , in the bridge or spare their lives and hold them prisoner instead . Gameplay . Whether the player kills the soldiers in the submarine or takes them hostage has no effect on the gameplay involving the submarine . If the player takes them prisoner , cutscenes involving the inside of the submarine , such as when finding the Key of the Ancients , will have them sitting on the side . While searching for the Huge Materia , the party will encounter a red submarine transporting it and become embroiled in an underwater battle . If the enemy submarine is not defeated , the Huge Materia is lost forever and the player can find the red submarine at the submarine dock at the Underwater Reactor . If the player defeats the red submarine examining its sunken wreckage on the sea floor will reveal the Huge Materia . The submarine minigame can be later replayed in the Gold Saucer ' s Wonder Square ; known as Torpedo Attack . If the player ' s submarine gets destroyed , Cloud and the party are saved by Mr . Dolphin and wash ashore in Junon . The player loses the submarine they had , but they can get another one by going to Junon and taking the entryway previously guarded by a dog to the Junon Submarine Dock . This is the only way for the player to get a red submarine ; otherwise their submarine will be gray . The submarine can also be used to explore the ocean in the center of the world map . If the submarine touches the Emerald Weapon , a battle initiates . The submarine is required to get to the Gelnika , and is needed to obtain the Ancient Key necessary to progress through the game . There is a glitch concerning the submarine , where if the player dismounts a chocobo next to the submarine and immediately gets into the sub , they can cause the submarine to get stuck on land . Locations . Both submarines share the same layout , though the torpedo room can only be accessed in the gray submarine . To access the room one would have to fail the submarine mission , and it is this same criteria is also necessary to be able to see the interior of the red submarine .