Walkthrough
Just north of the Water Path is the Green Path. As the name suggests, this small path is full of plant life. Because of this, only one lone Pokemon Trainer can be found here. Oddly enough, the only Wild Pokemon located within the Green Path can only be found within the the water. If you're looking to find loads of Wild Pokemon in this area, you will need to head into Pattern Bush, which just so happens to be found in the Green Path.
Wild Pokemon
Surfing:
Tentacool (95%): Levels 5-40
Tentacruel (5%): Levels 35-40
Magikarp (100%): Level 5
Horsea(FireRed)/Krabby(LeafGreen) (80%): Levels 5-15
Magikarp (20%): Levels 5-15
Horsea(FireRed)/Krabby(LeafGreen) (40%): Levels 15-25
Qwilfish(FireRed)/Remoraid(LeafGreen) (40%): Levels 15-25
Gyarados (15%): Levels 15-25
Seadra(FireRed)/Kingler(LeafGreen) (4%): Levels 25-35
Psyduck(FireRed)/Slowpoke(LeafGreen) (1%): Levels 25-35
Pokemon Trainers
Psychic Jaclyn: Level 48 Natu, Level 48 Slowbro, Level 49 Kadabra
Pokemon Trainers - VS Seeker Rematch
Psychic Jaclyn: Level 52 Natu, Level 52 Slowbro, Level 54 Kadabra
Items
Ultra Ball: ItemFinder