In pokemon sapphire there is a gym that is locked what do i do?

Answer 1

Are u talking about the Sootopolis gym? If u are here's what to do:

Exit Tate and Liza's gym by using the teleporter over to the right, walk out of the main door. Run back to the Poke Center and heal. Exit the Poke Center, head west, then go north, enter the house, this is Steven's house, he will give you HM08 which contains Dive. Run back down to the shallow water, surf out on
your Pelipper, and swim around in the water, catch a Tentacool and teach it Dive. Swim into the water, go south, you will come to a gigantic area you can dive in, follow it as long as you can, you will see a cave, go in it. Inside is the Submarine Explorer 1, inside this room, re-surface, swim to the sand and run through the next cave. Enter the cave, go left, break the rock to the
north, then push the moveable rock to the point where the breakable rock was. Go east, then push this rock east, continue north, challenge the Team Magma Grunt here. He will use a lv37 Poochyena, use Gravler's Magnitude, next is a lv37 Numel, use Gravler's Magnitude. Go up the steps and challenge the Grunt
to the south. He will use a lv38 Numel, use Gravler's Magnitude. Head south through the cave opening, head south, you will come to two rocks side by side, use Gravlers Strenght to move the rock, move the rock on the right, push it two steps south, take one step left and break the jagged rock. Continue south
and go through the door. Head east, then north, go through the cavern door, in, push the boulder you come to north, go west, push the rock you come to east, then go south, exit this room, and re-enter. Push the rock north, go east, then north, go west, push the rock over to the west, break the rock to the north, go north, push the rock to the north, go west, break the rock, push
the next rock west, then go north through the cave opening. Use surf to get to the ledge on the left side of this room, if you go down the middle area it will take you back to the start. Go through the cave, move the boulders in this room, challenge Magma Admin Courtney, she starts with lv38 Camerupt, use Pelipper's Water Gun, next is a lv38 Mightyena, use Gravler's Rock Blast. After the battle continue past Magma Admin Courtney, go through the cave opening. Push through the rocks in this room, go through the opening on the other side. Run east, check the Item container, it is TM26, or Earthquake, continue south, down the steps. Follow this as far as you can, you will soon be stopped by Maxie yelling at you. He will challenge you, he uses a lv41 Mightyena, use Gravler's Rock Blast, next is a lv43 Camerupt, use Pelipper's Water Gun, he will end the battle with a lv41 Crobat, use Gravler's Rock Blast. You will go outside, swim west to Sootopolis City. To enter the city you must dive into the deep water and find the cave entrance, on the inside surface. Swim to the left inside the city, go up all the steps, you will come to Steven, he will introduce you to Wallace, this towns gym leader. He will then have you follow him. When you stop enter the Cave of Origin.

Run forward, go through the next opening, have your Lotad use Flash. Go left and down the ladder. Go south, west, then north down the ladder. Go through this next room and down the ladder at the end. In this room head north, check the Item container, it is HM07, or Waterfall. Continue east down the ladder. This room will have a Pokemon, run so it can see you, it will come over to you and challenge you, it is a lv45 Kyogre, now if you still have your Master Ball, which you should, throw it at this Pokemon and it will get an instant catch no matter what. Exit the Cave of Origin. Now heal your Pokemon and make sure that you have the lv45 Kyogre in your party in place of Castform. Enter the gym.

Sorry its so long!!

Answer 2

u g2 find team aqua's underwater hide-out, located near sotopolis. theres a huge dark water spot, and dive. ull find an entrance. go in it, ull see the submarine. from that place, use dive again. now, just beat the team members and reach the place where kyogre is sleeping. team aqua awkaes it, and u now have to save the world by either defeating or catching kyogre. after this is done, u can access the sotopolis gym