Johnny the sea turtle is back in the Gulf of Mexico where he belongs today. The rare Kemp’s ridley turtle was found three years ago washed ashore in the Netherlands, where he had apparently been carried by a wayward current. The cold, disoriented turtle, who ways 68 pounds, was cared for by Dutch marine specialists, then shipped to Mote Marine Laboratory on the Sun Coast for further treatment. Yesterday, with about three hundred well-wishers to see him off, Johnny swam into the surf off Lido Key and back into the Gulf where he belongs.