As soon as you enter the route, talk to the Parasol Lady and she'll give you an item depending on what time of day you talk to her. She'll give you the Damp Rock if you talk to her in the early morning, the Heat Rock if you talk to her in the daytime, the Smooth Rock if you talk to her in the afternoon and early evening, and the Icy Rock if you talk to her at night. She'll give you only one rock per day, though, and only one of each rock. These extend the duration of the respective weather condition from 5 turns to 8 turns instead.
There's a Big Pearl that requires Surf in order to reach by the Fisherman.
The Parasol Lady further west has three Castform that she'll battle you with in a Rotation Battle. They're all at level 60. A Lass right above her has a Shelmet L60, a Slugma L60, and a Gastrodon L60.
To the north is a Fisherman using a Barboach L60, a Whiscash L60, and a Stunfisk L60. To the east, you'll find another Parasol Lady, who will fight you in a Triple Battle. She uses a Jolteon L60 (middle), Ludicolo L60 (left), and a Castform L60 (right). There's a hidden Max Repel nearby her, plus, more importantly, the entrance to the Moor of Icirrus, an optional area to visit along the way.
Heading to the west of the Fisherman will lead you along a wet path. In the northwest corner, you'll find a Youngster using a Palpitoad L60, a Croagunk L60, and a Vaporeon L60. To the north of him is TM36 (Sludge Bomb), a decent Special-based Poison-type attack with 90 power and a chance of inflicting poison. Over to the east of that is a Nest Ball.
Directly south of the Youngster, across a puddle of water and in the middle of some flowers, is a hidden Rare Candy, which you should definitely pick up. Keep going east and you'll find the entrance to Icirrus City!