After checking out the Battle Royals at the Battle Royal Dome in Royal Avenue, you head northeast to explore Route 7.
In Route 7, there is a Captain's barricade up ahead, so you can't go through the tunnel right now. But you can go up to a ramp that leads down to the beach. Stoutland can find a hidden Net Ball on the south part of the beach. You can ride Lapras in the water.
In the water, you can battle Swimmer Dakota. He has a level 19 Surskit and a level 19 Dewpider. You get 456 Pokédollars for winning.
If you go north in the water, then to the beach to the left, go down to the south part of this beach to find a hidden Pearl on the rock.
There is a green sparkle on the north part of this beach.
If you go northwest along the path, you can find rustling sand. Go up to the sand to battle pokémon.
Go farther north and go up the ramp to find a Max Repel.
Go back down the ramp. In the nearby water, you can battle Swimmer Tiare. She has a level 19 Alomomola. You get 456 Pokédollars for winning.
In the eastern part of this bay, you will see an Antidote underwater. Just swim over it and press A to get it.
Nearby, you can battle Swimmer Casey. He has a level 19 Mareanie. You get 456 Pokédollars for winning.
You can go south from there to find a separate beach area. When you get there, you can battle Swimmer Vanessa. She has a level 18 Shellder and a level 19 Corsola. You get 456 Pokédollars for winning.
Go south from Vanessa and you find a small pool that you can fish in. To the left of that pool, you find TM73 Thunder Wave.
That is all that you can find in Route 7, so when you are ready, go west to Wela Volcano Park.