Exbel peninsula

Exbel Peninsula is just south of Exbel Coast. You can get there by completing Mineral Cavern or by using Surf down from Kingler's Cove. You can either choose two routes, where the North will take you back to Grassroot Town, while the South will take you to a small port leading to South Outpost Island if you have Surf. If you use Surf or press enter while your Surf Pokémon is active, it should say, "Water currents lead into the distance... would you like to use Surf?"