Jetskier,
Glad to hear your friend Debbie is fine. That is a scary situation, mainly because no one can forewarn this before the tragedy. At least with a Hurricane or a Tornado, you get some warning to prepare.
Here is a link for more info and causes of sinkholes for Florida. Save Mickey Mouse, don't let him disappear.
http://www.swfwmd.state.fl.us/hydrology/sinkholes/