Find: Battle Trumpet & Scimitar.

Enter Junon and talk to the Shinra soldier in the far back of the town. Pay him 10 gil to use the elevator. Push the button to go up, then exit. Go out the door to your left to get to the streets. Take the street down towards the screen. Run off the screen and then up under the bridge. Once under the bridge, run down to the left where the soldiers are practicing. Follow them and enter the door on the left. Once in the elevator, you have to fight two members of the Submarine Crew. During any battle with the Submarine Crews, you can win the Shinra Beta Armor.

Take the elevator down and exit. Here you will fight two more guards. Then run to the right and exit. Run down the stairs and keep going left. Go out the door, then run right. Save here, and go out the door. Take the elevator down, run all the way up to the door, and enter the underwater tunnel. You may want to get the Guide Book here (if you are going to get the Underwater Materia; you do this by morphing a Ghostship).

Follow the tunnel around to the right and enter the reactor. Push the button on the far left to use the pressurized elevator, then exit. Run along the catwalk to the left and enter the door. Save and exit to the top right. Run past the guards to fight. Run right and do it again. Enter the door and follow the catwalk to the right. Watch as the Huge Materia gets hauled out. Run to the right to get to the sub. The Huge Materia gets loaded into the sub and the door closes. Talk to Reno, who makes you fight a boss.

This strange looking machine is mean and fast. He can grab two of your characters in his arms. The characters in his arms will get hurt when you hit him. Destroy the arms first, then the Carry Armor. Use your strongest Summons, and Lightning attacks work well. Cure often, because he hits fast.

After the fight, grab the chest on the left for a Battle Trumpet, then run to the right. Go up to the sub and get the Scimitar from the chest, then go left for the Leviathan Scales. Try to board the sub. Talk to the guards to fight them. Once you climb in, fight again. Save, then enter the door to the bridge. You can either fight the guards here or take them prisoner. Either way, it makes no difference, except that if you fight you can steal the Shinra Alpha Armor from the Captain.

Pilot the sub after reading the instructions. Defeat the red sub in less than 10 minutes. You get the Shinra Sub. Either enter Junon and go to the airport to see a plane take off, or go down to the sunken red sub and get the Huge Materia. If your sub blew up, return to Junon, and go under the bridge. Work your way to the elevator where you fought the guards, and talk to the dog at the bottom. You will go to another sub. Hijack it. If you did not destroy the red sub, the Huge Materia is gone for good.

To get to the red sub, pilot your sub south to as far as you can go. To the west should be the sub. Run into the red sub to get the Huge Materia.