Dave -- Judging from my experiences around Charlotte Harbor, which I believe is north of Naples, the rays are all over the place down there, so take the threat seriously. We spent an afternoon at a place called Burnt Store and the bottom was carpeted in them. I remember seeing my fishing partner backing up in horror as one came straight at him. I also had one sidle up to me in the back country. I understand they're only a danger if you step right on them (hence the recommended shuffle step while in the water -- it works at spooking them) but you'll still get the chills when you round a small point in the mangroves and one is a rod's length away and flapping towards you. No waders needed, but I'd suggest flats boots as Tevas are no help if you're on oyster shells -- when you step on a pile of them they'll wrap around the top of your foot and slice you up pretty good. Also you might want to check out Capt. Pete's link under the "flies for Captiva" thread.