Pokémon FireRed and LeafGreen/One Island

Seafoam Islands
'''Welcome to Seafoam Islands, where the next part of your journey takes place. You'll split your time among three islands, named One, Two, and Three Island. It's here that you'll have the oppturnity to catch Moltres and Articuno of the famed bird triology. For now though, spend some time exploring.'''

Arrival
When you first arrive, you'll be escorted by Bill to the local Pokemon Center, where you'll meet with Bill's friend, Celio, who's in charge of getting the local P.C. network up and running. You'll be given a Tri-Pass (used to ride the boat between the islands, a second page to your map that shows the Seafoam Islands, and a meteorite to give to a Two Island local, although you won't be able to do anything with it for now.

One Island
One Island is a small community, consisting of a Pokemon Net Center with an unique machine (one that lets you trade between Ruby, Sapphire, and Pokemon Coliseum, but you won't be able to use it for a while). There's no Pokemart in town (or on any of the islands), so you'll need to return to the mainland to stock up. Visit the few residents on the island and head back to the ferry and set sail for Two Island.