I saw a profile drawing about a year ago. It was a spring in the Gulf of Mexico, somewhere in the Naples/Tampa vicinity, and it appeared to be a very large, and deep (400ft+) cone, with the smaller end at the top. The entrance was deeper than 100ft, but that's about all I can remember.

I'm not looking to dive it, but I would like to read up on the subject. Perhaps someone can throw out some names that will jog my memory, or point me in the right direction.

Thanks.