I was down at the Chittendon Lock in Seattle this morning. the smaller lock is closed for annual maintenance. the Corps of Engineers called in the Navy divers for some help. A big pile of silt had built up outside the downstream gate and the emergency gates had some problems. Shot 1 is the Navy dive boat. If you look carefully in shot 2, there is a diver sitting to the left of a red seat in full dive gear and hooked up to the air system. He is the "emergency diver". The entire time the other two are down, he ahs to be ready to go over immediately in case a diver gets in trouble. the last shot is the two working divers finally surfacing. They used shovels, a high pressure water hose and big suction pumps to stir the silt and then pump it over near dam spillway. Those two divers were underwater working for 4 solid hours without surfacing. The water there is about 20-22 feet deep. I don't have much underwater experience, but seems to me that 4 hours underwater shoveling, wrestling suction lines and repairing the door must require these guts to be in pretty damned good shape.