From StrategyWiki, the free strategy guide and walkthrough wiki

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.

• Cooltrainer Ruben
  • Shiftry (lvl. 34)
  • Graveler (lvl. 34)
  • Loudred (lvl. 34)
• Cooltrainer Alexa
  • Gloom (lvl. 35)
  • Azumarill (lvl. 35)

In between the islands to the south is a third trainer.

• Triathlete Katelyn
  • Staryu (lvl. 36)