We took a pontoon plane from KW to Dry Tortugas and that was a great day, very good snorkeling off the beach. From the air you can see the sand dunes that are reportedly constantly shifting in that area and understand why Mel Fisher had trouble finding the wreck upon his return...
Met a couple from TX who were roughing it there (off the grid) for a week or two - took the ferry in, no electricity, running water, etc, and they described the walk to the restroom at night with dealing with hundred of crabs...A unique getaway!