The first area of pokemon-infested sand you’ve found in the game, this sideline to Route 4 offers a chance to level up a bit and snag some new team members before facing Colress for the first time.  The sand around here contains a few interesting things- Trubbish, Sandile, Scraggy, and Darumaka at levels 14-17.  Sandile provides you with a nice ground-type option if you haven’t got a Drilbur from the Relic Passage, and between its moderately greater bulk, interesting potential Moxie ability, and Dark typing, it could help you out in some very different ways from the mole.  Scraggy is a hugely tough customer, always taking loads of punishment to lay out and with few exploitable weaknesses, and Darumaka becomes the fairly powerful Darmanitan.  While Darmanitan isn’t as all-around-awesome as Arcanine, which evolves from the Growlithe you could pick up earlier on, it’s a bit more focused and has some access to moves that escape the fiery dog, as well as being a bit faster.

You’ll also run across a police officer shortly after entering the sand, whose Herdier doesn’t like you- so he attacks!

Battle: Officer Braven (640 Poke)
Opponent: Growlithe Lv 16, Herdier Lv 16

Past Officer Braven is a set of stairs down to a seashore, where you can find a Mysticwater and a pair of fishermen.  The fisherman to the North is eager to battle....

Battle: Fisherman Hubert (544 Poke)
Opponent: Basculin Lv 17

...as is his associate.

Battle: Fisherman Andrew (540 Poke)
Opponent: Psyduck Lv 16, Basculin Lv 16

Colress tells you he’s been waiting for you, and explains that the ‘rocks’ blocking the path are, in fact, a group of Crustle that are sitting there and impeding anyone who wants to get by.  Waving a device in the air, Colress prompts the Crustle to all get up and wander off.  He wonders briefly if the Crustle were just tired, or what- but refocuses on what exactly he was here to say to you to begin with.  Team Plasma, he explains, felt that pokemon should be separated from humans to realize their potential, but he disagrees and feels that it needs to be humans that bring out the full potential in pokemon.