In 1965 Halbert Fischel together with Tony DiChiro and Larry Cushman and Dave Joss designed and tested a cryogenic diving system capable of taking the diver to 307 meters of depth with diving times up to 5 hours. The units used a technology with a cryogenic scrubber system. The energy for reaching these low temperatures was achieved by taking liquid nitrogen during the dive carried in 1 cylinder. The technique is not commonly in use anymore. The russians build a similar design that can be seen here. Please enjoy this great story