Paul,
I have dealt with Swiftmud, Southwest Florida Water District, when digging my pond in Sarasota, you probably have heard of them since you are in Tampa. Both agencies enforce water usage laws as well as county ordinances. They are the LAW and like all big agencies are difficult to deal with on personal matters. If you have talked directly with an agent I would follow his advice to the letter. I did find, as is usual, that once I got somebody's name, and kept talking to that person about my plans the friendlier and more helpful they became. The application for a larger lake will cost money to be sure so if you want a 10 acre lake get ready to buy the permits. Or get the 6 acre permit and keep digging. (not my suggestion)
Toby
