In Mossdeep City, Steven will give it to you.
Defeat the 7th gym leader
You get it
you can find dive balls at the mossdeep city pokemart
find it using dive
you have to find the darkest patches of water to dive down in
you have to beat mossdeeps gym leader and get dive. then dive wherever you can and talk to the boulders
Dive underwater and find the team aqua base (if you beaten the psychic gym)
you get from the gym leader in mossdeep city NO YOU DONT I WENT THERE AND I BEAT THE TWINS I DIDNT GET DIVE
you can find it by using dive in route 124 and 126
there's no hm dive in firered.so that means you can't find it.but you can find it in Pokemon ruby,sapphire,emerald and more.
You don't need a Red Shard for Dive.
between route 134 and 133. find the dark spot to dive
You get the abilty to use the move Dive from Tate and Liza in Mossdeep and then you can teach your Pokemon to Dive! X3 POKEMON-1001
After you find the stolen submarine in Pokémon Emerald you must go to Mossdeep city. There you will obtain the HM Dive.