Information from Windmill World website (there's also some links to more pictures on that site)
"Carl Fisher was the leading light in developing Miami Beach into a vibrant and popular destination in the 1920s. At that time he built a casino hotel at what is now the South end of Miami Beach, with large swimming pools, known as the Roman pools. On the seaward side of the pools was a large windmill, which it's been suggested was utilized to pump seawater into the pools.
The windmill, regularly described as a Dutch mill (but that's just to make it clear that it was not simply a skeleton windpump, or wind engine) was a tower mill which pictures show in multiple orientations, so its clear that the cap and sails could revolve. However, I've not come across any pictures that prove that the sails were workable - most pictures show a very flat cross as shown above, which tends to suggest its major use was just as a advertisment for the casino. Some images do show a fantail atached to the cap, so its quite possible that it was a working system once, but later replacement sails may simply have been ornamental. "