Pokémon Ruby and Sapphire/Route 108

Route 108 has a large, abandoned ship midway. You'll have to battle some trainers to get to it.

Items

 * Rare Candy - hidden on a rock on an island to the southeast of the Abandoned Ship
 * Star Piece (Emerald only) - on an island past Cooltrainer Carolina and Sailor Cory

Trainers

 * Swimmer Tara
 * Swimmer Jerome
 * Swimmer Missy
 * Swimmer Jerome
 * Swimmer Missy
 * Swimmer Missy
 * Swimmer Missy

Go north to find the Abandoned Ship.