Florida recognizes valid registration certificates and numbers issued to visiting vessel owners by other states for a period of 90 days. An owner who intends to use his vessel in Florida longer than 90 days must register it with a county tax collector. However, he may retain the out-of-state registration number if he plans to return to his home state within a reasonable period of time [he must still register the boat in Florida, however].
Regulations similar to these are typical in most states and apply to car license plates as well. Among most all states with these regulations there is not personnel staffed to record these vessels or cars and note the dates of their presence within the state. I have heard of ocassional scans made through employee parking lots for out of state auto plates. Once again, there is nothing specifically unique about Florida having regulations that require boats or automobiles remaining in the state to have a state registration. Very rarely, is a seasonal cruisers ever confronted with this issue. Take care and joy, Aythya crew