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I've seen similar elsewhere (but they are very widespread) and they are typically moonbeam jellyfish. Harmless.
Freeze 43, you are speaking of Moon Jellies (no beam). They are worldwide, common in Florida, the Bahamas and the Caribbean. They are mildly toxic and cause a slight itchy rash in sensitive people, much less so than other species.
Scuba_Noob, I think they would be very tasty for turtles. I, however, would not want to eat one. Don't know if they are palatable or edible for people.