That would be waterfall which can be found in icefall cave on four island.
This means that your Pokemon probably has learned fly. This move is not allowed to be transfered from game to game by migrating. You should take rayquaza to the move deleter and have fly deleted and then you can migrate it to diamond and teach it fly then.
Hidden Move 8.
Use the pokeflute.
RFDHDF
there is no such move as stength
Dive is not a hidden move in leafgreen.
the move deleter is right of the Pokemon gym in fuchsia city.
The 5th hidden move is defog the 6th is rocksmash the 7th is waterfall and the 8th is rock climb. HAPPY TRAINING!
In Pokemon Fire Red, you use Hidden Moves by opening you Bag while in a field outside of a battle, going to Key Items, press the A button on the item, TMs Bag, and then go to any Hidden Moves you want to use. Press A on it until you are to choose which Pokemon to teach it to. After you have your choice, decide which current move you wish to forget so the Pokemon can learn the Hidden Move, and you're done! The Pokemon will have known the HM that you wanted it to learn.
Use the HM move Strength.
There are not many glitches in Pokemon FireRed. There is one rather nasty glitch though involving roaming Legendary Pokemon. In Pokemon FireRed if a roaming Legendary Pokemon escapes battle with the move Roar it will disappear from the game rather than move to a new location.
Use the pokeflute.