Where do I go after delivering the letter to Steven in Alpha Sapphire?

Playing Pokémon Alpha Sapphire, I gave the letter to Steven and talked toMr Briney, got 2 badges and I’m stuck. What do I do now? I can’t get to Verdanturf or Mauville city (no bike or Rocks Smash)


After beating the Rustboro Gym and helping the Devon employee, you meet Mr. Briney. After that, you'll be able to sail with him to and from Dewford Town. This is where you deliver the letter to Steve (in the cave) and compete in the Fighting type Gym. After this, Mr. Briney can sail you Slateport city, where your journey continues.