Surf's up dude! Having obtained the Rumble Badge, you can now use HM Surf to your heart's delight, even outside of battle. If you cast your mind back, there were some bodies of water earlier than you could interact with, but couldn't move onto without Surf.
When you have a spare moment, it might be worth hopping back to those old places to find new Pokemon (while surfing) and items. That said, some of those places are quite faraway, so we recommend going back after beating the next gym , so you can use Fly to quickly get around!
This area is hardly worth mentioning in detail, but to those who are curious... As you come in from Santalune Forest, go west and Surf across the water for a Dawn Stone . If you didn't come back to use Cut before, go further north along the ground Route and you'll find a Cut tree. Beyond is a Revive .
Route 8 Oceanside
Let's come from Ambrette Town. Head north along the route to the Mago Berry tree. (Grab another if desired.) Head onto the water and Surf northwest. You should be able to encounter a Sky Trainer from the island: although you may need to stand northwest from the berry tree.
If you head north-northwest of his island, you should see a sandy island where you can examine a rock for a Heart Scale . North of there, you can Surf and battle a Swimmer. On the nearby island, you can find TM19 - it teaches Roost.
Roost is a move for many Flying Pokémon that makes them land and lose their Flying-type designation briefly while recovering HP. It may seem stupid, but think of what you need to do in a pinch against, say, Raichu or somethin'.
Another Swimmer is going around the rock formation to the southeast, so battle him, too. A while to the north, within the borders of Cyllage, you'll find a house on an island. It gets electricity, too - there's a TV. Anyways, the kid within will hand over a Charti Berry , which weakens super-effective Rock-type moves.