Few words were spoken as we took in the sites. We rounded St. James City, the opposite end of Pine Island and Bokeelia. Soon we banked right over the Sanibel Causeway, over the bay heading toward Upper Captiva and Useppa Island, then made a hard left to circle the island tip just offshore, heading back in the direction of Fort Myers Beach, now three islands away. I looked out for airplanes, knowing Upper Captiva has an airstrip — no traffic. We flew onward to Sanibel, just offshore at 200 feet, and suddenly, out of nowhere, all hell broke loose. There was a very loud bang! A vibration shook the little airplane and us violently. It was hammering so severely, I could not focus on the instruments. It vibrated so badly when Paul asked "What the hell was that?" that his diaphragm sounded like it was pulsating at a high frequency, like someone was beating on his chest as he spoke. When I responded with shock and fear, I was surprised; I sounded the same. "I don't know!"