Florida Casual... khakis/white linen pants, loose fitting but nice collared shirt (Polo, Tommy Bahama, Cubavera, etc) If it's in South Florida a Guayabera would be appropriate. I typically wear Brown leather sandals or nice Birkenstocks when I have to dress like that. A jacket/sport coat is acceptable as well, and I would suggest it if it's near the water.
Bear in mind that Florida is rather diverse and different cities/regions may have different definitions of "Florida Casual"