Tou have to turn on all of the switches and then go to where you started (the entance door) and then you take the pointy arrow pad on the left and fite the gym leader
To defeat or "beat" the 7th gym leader in Pokemon sapphire there twins and they have a solrock and a lunatone to beat them I suggest about level 40-50 water types.
The third gym leader in Pokemon Sapphire is Wattson and he is located in Mauville City.
In sapphire, the 5th gym leader is your dad, in that city after Oakdale.
The 8th Gym Leader in Pokémon Sapphire can be found in Sootopolis City.
You can with AR.
The 6th gym leader in Pokémon Sapphire is found at the Fortree Gym. The name of the gym leader here is Winona.
In the lavaridge town gym.
the fourth gym its a fire gym
mauville city gym leader wattson
The leader is Falnery, she uses fire type pokemon.
i think you get to the underwater cavern after beating the 7th gym leader
Mossdeep City