Go to Daytona - drive on the beach - about as close as you can get!
Parking is all around the open access beaches, some offer designated car parks, others have parking a block or so away. Some areas have a charge for parking at the beash - as at West Palm Beach, but there are alos loads of beaches open to all and free parking that also offer lifeguards on duty, access to the nearby cafes and so on.
National parks (like the John Pennekamp NP in the Keys) may be the best bet if you have a worry about crime as above - they offer parking with potentially better security....and sailling, scuba gear hire, clean beaches, etc etc
In short, go , park (check for any fees) and have fun...