Saturation dive training. Closed bell used for training commercial divers in closed bell operation for saturation dives. Saturation diving is where divers live in a pressurised environment at great depths for extended periods of time. The technique allows divers to reduce the risk of decompression sickness (the bends) when resurfacing. Here, the closed bell is being lowered from a support vessel into the water. This diving bell opens at the base when the required working depth is reached to allow the divers to work one at a time through a moon pool. It mates with a pressurised habitat to maintain the divers at working pressure for up to a month at a time. They are used in deep water oil and gas operations worldwide. Photographed at the Underwater Centre,