"The Cobra" was an experimental diving unit that was intended for military use as a "Fully Close Circuit Rebreather" using "100% Pure Oxygen". And as a "Semi Close Circuit Mixed Gas Rebreather" using gas mixture called "Nitrox B" 60% oxygen & 40% nitrogen, "Nitrox C" 40% oxygen & 60% nitrogen, "Nitrox D" 32.5 oxygen & 67.5% nitrogen. "Heliox" Oxygen & Helium & "Trimix" Oxygen, Helium & Nitrogen.
Jill Heinerth, whose first job was a newspaper route in her home town of Toronto, Canada, is today a pioneer technical diver and instructor, a renowned explorer of underwater caves who owns a record for the deepest and longest cave dive, and a record for the longest dive into an Antarctic iceberg. Read the interview; http://www.xray-mag.com/content/jill-heinerth