One afternoon while visiting the Florida Keys I photographed my wife, Fyllis, swimming with stingrays and other denizens of the sea in a huge tank of water, then shoving live fish through an opening in a Plexiglas wall to feed hungry sharks on the other side. Driving back to our temporary home away from home, we passed houses fronted by mailboxes shaped like dolphins, manatees, and seahorses.     The island chain that stretches southwest from the tip of Florida combines encounters with Mother Nature’s magnificent handiworks with occasional touches of commercialism. Magnificent parks stretch out near shops selling sandals, shells, and T-shirts. Recreational vehicle and trailer lots are adjacent to upscale resorts.     Key West offers a variety of tempting things to see and do, from funky and fashionable to historical and hysterical. Fyllis and I also wished to check the claim that other islands boast attractions and …