Walter

Walter is the Water Gym Leader and a person that interacts with the player! He will teach you the Dive abillity.

When you reach his home (in Westport City) he gives you two quests:


 * Deep Sea Demo 1


 * Deep Sea Demo 2

You complete them by battling 3 trainers with six level 70 Water-Type Pokemon each, though there is a tp requirement of 10,000. After completing those two quests, he teaches you how to Dive and get ascess to Underwater.