The most egregious violation of responsible diving practices I've seen was when a NAUI group from Cape Ann, MA was visiting us in the Florida Keys. We went out with Lady Cyana Divers to Hammerhead Reef. I was buddied with a PADI instructor from Utah. He and descended to 30 or 40 feet under the boat. As we were pausing to check gas and adjust gear, steel 72 scuba tanks began raining down around us. Each tank landed on the coral like a WW II dud bomb. Unlike duds, these cylinders were destructive. The NAUI divers swam down wearing horsecollar BCD's and donned the tanks by kneeling on the bottom. I saw my buddy staring in disbelief with his hands on his head in a display of shock and awe.