Florida is a very friendly state. They love visitors and the money that you spend. You can keep everything you dig on the beaches. Even some state parks allow digging. The ones on the Atlantic ocean allow it but most inland do not. A simple call to the park will tell you. Once in a while they find Spanish cobs on the beaches below Kennedy. You can keep them. Here is a site that has daily info on that part of the state.
http://treasurebeachesreport.blogspot.com/
I do not know of any shipwreck items found where you are hunting though and no lease sites. You diving or water hunting? If you are diving then try calling the local dive shops for information on where to hunt and any regulations. Might pay off. Good luck!