Over the past two decades, diving technology has made a dramatic improvement. This is today’s rebreather. The rebreather has great advantages: For most CCR dive, gas supply is no longer a major consideration, compared to the traditional open circuit (OC) dive, the no-decompression dive time is greatly extended, which appeals to many photographers, and the impact to the surrounding environment is also reduced a lot, it no longer makes bubbles; what’s more, you breath warm and moisturized gas instead of dry and cold gas with OC. Rebreathers are welcomed by the technical diving field because it reduced the cost to a range acceptable to divers and allowed the exploratory divers to challenge the difficulty that the OC could not challenge.