We're about halfway through this route now! Return to the Parasol Girl below the sunbeds and gleefully stroll towards the sunbed. If you head left from here, you'll encounter a man with shades who will give you a rare item free of charge. Come back to him on another day for another item. Nice!
Past him, to the left, is a house; not a resthouse, sadly. Inside, there's an old man who will teach your starter Pokemon a powerful move . These moves are nice for doing major damage, but requires your Pokemon to recharge after each hit, so use them wisely if you learn them.
Back outside, continue past the house--yup, you can actually go behind it! At the very end of the sand, Surf into the water and head west. On the other side is another house, isolated from civilisation. Speak to the Veteran inside to aquire a Splash Plate and Draco Plate --both items for Arceus.
Go back to the sunbeds again and, this time, head north. A few paces away, you'll spot another Parasol Girl; this gal is lookin' for a fight, so have those Poke Balls (or mad stealth skills) at the ready...
Trainer Battle: Parasol Girl
Carry on north along the narrow sandbar, possibly disturbing the Fisherman for a battle.
Trainer Battle: Fisherman
Poor guy... actually, you can't hook Magikarp in this route or anywhere in Unova. So where did he get those Magikarps from!? Uh, anyway, at the end point you'll encounter a bald man who isn't looking for a fight.
Now this part is very sneaky. Surf to the right of the bald man and head north through the narrow gap in the rocks. You'll find that you can continue north, along the shoreline, towards a flight of stairs leading north. At the very top, navigate around to the south-west, where there's a boulder.
If you have Strength, use it to push the boulder into place, creating a shortcut to Lacunosa Town. Should you need rest, you can head there now and use the Pokemon Centre. Otherwise, go back a bit and continue north through the narrow path. Before long, you'll arrive at the Giant Chasm .
But if you want to explore the rest of this route, backtrack until you're with the bald man once more.
From here, turn left and follow the sand, maneuvering underneath the wooden bridge above. Immediately after passing the bridge, there's a Fisherman looking down. Interrupt him and he'll punish you with a Pokemon battle.
Trainer Battle: Fisherman
Continue left to the end of the sand and through the tall grass, then climb up the long flight of stairs. Up on higher land, cautiously make your way right. Circling a bunch of trees ahead is a Youngster.
Trainer Battle: Youngster
Having beaten or avoided him, go south from the clump of trees, onto the wooden bridge. On the bridge itself is a Lass with a problem... or a Wingull with a problem, rather. The poor critter has misplaced three Grams and you're the only one badass enough to find them.
For now, continue south along the outcrops and wooden bridges. On the second bridge down, there's somebody you can battle.
Trainer Battle: Artist
Upon passing the second bridge, you ought to notice an item lying in the corner of the final outcrop of land. Pick it up to find it's Gram 2 ! Nice job; return it to the Lass and she'll ask for the other two.
At this point you will need to backtrack a little. First return to the bald man who didn't ask for a battle for Gram 1 . He's standing along the northern shoreline, not too far away. Then go back to the Parasol Girl next to the sunbeds--again, the one who didn't want a battle--for Gram 3 .
With all three Grams in hand, the Wingull will leave happily, leaving behind TM89 U-Turn . With that good deed done, make your way north, past the circling Youngster. You will need to walk through a narrow patch of tall grass to continue.
Once you're free of the grass, there's a Lass looking back and forth for a battle.
Trainer Battle: Lass
Past her, to the right is the way to the Giant Chasm, provided you pushed the boulder earlier. To her left is the entrance to Lacunosa Town . Congrats! You just made it to the end of Unova's longest route!