first unlock both Groudon and Kyogre. if you get out of dive, you will see team aqua.. they'll talk for a long time then they will go. go to Sootpolis and then you will see Groudon and Kyogre fighting. You have to go to the cave of origin and talk to the person there. press sky pillar. then go to the sky pillar and wake up Raquaza. Then go back to Sootpolis and Raquaza will stop the battle then they disappear and then you will talk to someone then you can go into the gym
well i forgot
Go to Sootopolis.
The Pokemon league!
Emerald: He is the champion of the Elite Four; Juan is the Sootopolis gym leader. Sapphire/Ruby: He is the gym leader of Sootopolis.
You have to catch Kyogre and Groudon.
sootopolis city
sootopolis city
In the sootopolis city gym.
In Sootopolis City.Trainers and Gym Leader uses Water-Type Pokemon.
This is because you have to go in the cave at the top of the town then the gym will open.
by defeating juan at the sootopolis gym
To do this, you have to have beaten the gym at Sootopolis. To get there, you have to have beaten the gym at Mossdeep and the Magmas at the space center to learn dive. Once you beat Juan at the Sootopolis gym, he will give you it. Hope I helped! :)