CUMA (Canadian Underwater Mine-countermeasure Apparatus) (commercially called SIVA+) is a make of rebreather underwater breathing set designed and made in Canada for the Canadian Forces by Fullerton Sherwood Engineering Ltd to replace the Royal Navy CDBA.
Its Carbon dioxide scrubber, and oxygen container and diluent container (both spherical), and valves are in a backpack casing, but its breathing bag is exposed on the chest.It has the usual loop of wide corrugated breathing tubes running from and to the top of the backpack. It has a small bailout cylinder horizontally across the bottom of the breathing bag. It can be calibrated before the dive to suit planned diving conditions.
It is a self-mixing rebreather. A constant flow of oxygen is mixed with a diluent volume dependent on the ambient pressure. The deeper the diver dives, the more diluent is added, and thus the leaner the mix is. The correct setpoint is controlled with an electronic partial pressure measuring device. The CUMA is capable for diving to 90 meters = 295 feet. Its diluent can be air or trimix or heliox.
Its first prototype set was made in March 1987.(Wikipedia)