Find: Heaven’s Cloud, Escort Guard, Conformer, Double Cut Materia, 2 Megalixirs, Summon Hades Materia, Outsider, Highwind Limit Break (Cid), & Spirit Lance.

Please note that you do not have to do this section and if you want to, you can do this at any time after getting the submarine. You can continue on to Rocket Town, Wutai, or even go back to Cosmo Canyon.

To get to the Sunken Plane, take the sub up to the top. From Junon's dock, go straight west until you reach a peninsula with a beach. Go around it to the north and circle around south. Once you are in the small inlet, submerge and the plane is just to your south. Run into it in order to enter the plane.

Climb down the ladder and get the chest containing the Heaven’s Cloud on the left. Save, and enter the research room to the right of the save point. You better be prepare, because in here are some of the toughest enemies around. The three Unknown type enemies here can really mess you up.

Run right to the chest for an Escort Guard. Run left down the stairs and to the left wall. Go straight up and get the Conformer (hidden in a chest in the corner). Grab the Double Cut Materia hidden in the upper-right corner of the room, then return to the upper level. Run up around to the top corner to get a Megalixir from the chest, then leave. Cure and save again.

Run to the left and talk to Reno and Rude. You fight them.

Reno uses Neo Turk Light, which confuses its target. Ribbons are good to have equipped. Rude uses Fire2, Ice2, and Bolt2. These guys are quite fast this time around. By the way, you can steal the Touph Ring and the Ziedrich from them.

After the fight, walk through the north door. Get the Megalixir from the chest, then run around to the right. Climb down the stairs and get the Summon Hades Materia from near the helicopter. Get the Outsider and Highwind from the chests at the bottom of the screen, then get the Spirit Lance from the chest above on the walkway. Leave the plane.