One Island

Walkthrough
After defeating the Cinnabar Island Gym, Bill, the creator of the PC Box System, will appear on Cinnabar Island and will offer to take you to the Sevii Islands. The two of you will board his speed boat and will soon arrive on One Island. This Sevii Island is compromised of three different areas: Treasure Beach (south of main island), Kindle Road (east of main island), and Mt. Ember (north of Kindle Road). When you arrive on One Island, Bill will introduce you to his friend Celio, the same whom is creating a PC System of his own. Celio will ask that you take a gift to his friend on Two Island, allowing you to explore One Island, Two Island, and Three Island as you so wish as you complete the task.

Wild Pokemon
Surfing:
Tentacool (95%): Levels 5-40
Tentacruel (5%): Levels 35-40

Old Rod:
Magikarp (100%): Level 5

Good Rod:
Horsea(FireRed)/Krabby(LeafGreen) (80%): Levels 5-15
Magikarp (20%): Levels 5-15

Super Rod:
Shellder(FireRed)/Staryu(LeafGreen) (40%): Levels 15-25
Horsea(FireRed)/Krabby(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

Items
Rainbow Pass: Later Obtained From Celio After Retrieving Ruby For Him