Island of the Giant Pokemon

As our heroes and Team Rocket beat the odds by surviving the sinking ship, they are dragged into another potentially deadly situation when they are attacked by the ferocious Pokemon, Gyarados. One Gyarados becomes many and Ash, friends and foe are swept up in a tornado landing them in various locations on an island. Ash loses Pikachu and the Poke Balls containing Charmander, Squirtle and Bulbasaur. Jessie and James from Team Rocket, who land in another remote part of the island, also lose their Pokemon. Thus both Pokemon and their masters are left searching for each other on this strange island, inhabited by gigantic Pokemon. Where could this island be?