After the 7th gym, surf around and when you see dark spots in the water, press A and use Dive. Then find a huge block with no wild grass, enter a cave door underwater, then go back up. You should be in Sootopolis City (water is light blue there) the gym leader there is Juan, who specializes in Water Types.
fortree
at the gym
pryce the ice type gym leader
fire
slate port does not have a gym
In Pokemon Sapphire, Ruby and Emerald the 7th Gym that's located in Mossdeep City has Psychic type Pokemon.
Water, dark and grass Pokemon
sootopolis city, after u awake rayquaza. the gym leader is juan, changed from ruby/Sapphire Wallace
Press the switches to move around the statues and use the portals to the navigate your way to the gym leader's.
The seventh gym badge in Emerald is located in Mossdeep City.
Twins Liza and Tate in Moss deep City, they use physicic Pokemon
get a pokemon, then you train it, get it really strong, and beat th ecrap out of all the 7th leader's pokemon. Its easy.
the seventh gym is at sekka city
You have to surf from Lilycove to Mossdeep city so you can challenge the 7th Gym Leader, The psychic twins, Tate and Liza.
The Fortree gym.
there is no gym at pacifidlog
In the mahogany gym