Saturation diving, also known as mixed-gas diving, is the highest level of commercial diving, working in depths past 164 feet (50 meters). Saturation diving is intense work, dangerous and demanding, requiring physical and mental stamina, as well as extensive dive training. Saturation divers wear hot-water, breath a mixture of helium and oxygen, and descend to the extreme depths in a dive bell. Before returning to the surface, saturation divers must be slowly decompressed to avoid the phenomenon known as the “bends.” Becoming a saturation diver requires intense training and is best accomplished in a series of gradual steps.