Route 115 is an ocean adjacent route which is seperated into two parts. The south part, which contains the entrance to Meteor Falls and an exit to Rustboro City, is the main part of the route, but contains no wild Pokémon. To get there, you need to Surf to the north where many strong trainers and Pokémon exist

Terra Cave
In Emerald, there are rare occasions where strong sunlight will appear within the route and open up one of two caves which gives access to Terra Cave. They are located as seen here

Special Moves used in Route 115:
Surf
Rock Smash