The term, hybrid system, is used to define a diving system that embraces both scuba and surface-supplied technology. A system of this nature was developed by Innerspace Systems, a Gulf Coast commercial diving company, in the late 1960s and successfully used for selected commercial diving tasks in the early 1970s. The primary gas supply system is a closed-circuit scuba on the diver. Consequently, a very low volume of gas is used for any given dive. Consumables cost only a few dollars per dive. The makes the system very attractive. Gas is re-circulated though a helmet or mask. The diver is also supported from the surface by a small umbilical. The umbilical can provide an emergency gas supply from the surface to a demand regulator on the helmet or mask, voice communication, system monitoring, depth monitoring and hot water for a suit (as needed). Modern technology should be capable of developing monitoring electronics that can feed information such as PO2, cylinder gas pressures, carbon dioxide level, and depth to a surface console display. Properly designed and proven through rigorous testing, this system could be the missing linka cost-effective, compact, portable diving system to more satisfactorily support a scientific diver at 300 fsw (92 msw).