Pokémon Ruby and Sapphire/Route 128

Trainers
Route 128 is a wide passage of water. There are two small islands on either side of the dark stripe of water that leads south. On each of them is a trainer.

In between the islands to the south are more trainers.

Items

 * Heart Scale - hidden on the smallest northern island
 * Heart Scale - hidden on the island that's east of the ring-shaped islet
 * Heart Scale - hidden on the south side of the southwest island
 * Protein (underwater) - hidden on a rock at the dive spot of the ring-shaped islet
 * Pearl (underwater) - hidden on a rock at the farthest-east dive spot