How To Get The Sapphire In Pokemon Leafgreen?

I have plenty of experience.  First of all, you must have beaten the elite 4 and have gotten the ruby.  You also must have obtained the rainbow pass from Celio.  Just follow these easy steps:
1. Use the Rainbow Pass to take the ship to 6 Island.
2. Go to the right [east] side of the island. You will be on the Water Path.
3. Use surf to surf as far down [south] as you can go on the Water Path.
4. Step back on to the land to your left. [West]
5. Walk around in the Ruin Valley, until you can go up the stairs.
6. From the stairs, you will see an old ruin with water around the back of the building.
7. Walk up to the door of the building and use Hm.1 Cut on the door.
8. Go inside.  Then fall down the hole.
9. In this room, you will see four holes. Fall down the one on the top.
10. You will again see the same room as the last one.  This time, fall down the hole on the left.
11. You will see the same room.  Fall down the hole on the right.
12. The same room again.  Fall down the hole on the bottom.
13. You will be in a room with the sapphire in the middle of it.  But when you try to take it, a mean scientist takes it from you, and runs, but he does tell you the other password to the Rocket Warehouse, where he is hiding.
14. Take the ladder out of the room. Then exit the ruins.
15. Fly back into town and take the ship to 5 Island.
16. Stock up on healing items. (Optional)
17. Go into the 5 Isle Meadow and enter into the Rocket Warehouse.
18. Use the arrows to get to the scientist.
19. Take the sapphire from the scientist and exit the building.
20. Fly back to town, take the ship to 1 Island, and give Celio the sapphire!  Hurray!