Southern Island

From the Sonic News Network, the Sonic Wiki

You may also be looking for South Island, the setting of Sonic the Hedgehog (16-bit). Sonic the Hedgehog (1991)

Southern Island is the birth place of Marine the Raccoon. She has always lived there. It's also home to the Coconut Crew, a bunch of koalas who are Marine's friends.

It appeared in the game Sonic Rush Adventure.