Hmmmm...I don't want to give away too many secrets (I am writing "The Crestview Conspiracy" based on unpublished true events) but if it is just a minor part of your story, study up on the Atlantis / Burmuda Triangle connection and modify it for you.
Also, read The Hollow Earth by Raymond Bernard. It's an awesome story you will enjoy.
The Devil's Triangle and hollow earth theories may not be as far-fetched and fantasy as one would think.....