In the 1950s, development of the scuba unit revolutionized diving (it was next generation diving), and its technology continues to develop apace. Modern underwater vehicles and other equipment is sleek, lightweight, and colorful, and advances in the efficiency of diving rebreather systems are transforming diving once again.
One of the most notable recent advances in modern dive equipment is the use of head-up displays in masks, which are similar to those used by military pilots. Essential dive information is sent via radio frequency from the tank to the mask, where it is presented on an LCD. Masks with an integral radio communication system, which allows divers to talk directly to one another, are also available.
Advanced synthetic materials have made dive equipment stronger and lighter, and have been used in the development of diver propulsion underwater vehicles (DPVs) that are smaller and easier to handle.
Underwater Vehicle.The breathing observation bubble (BOB) is powered by an electric motor and has a top speed of 2.5 knots.
In the last decade, diving rebreather technology in the same way as underwater vehicles has become available to the recreational diver, representing the most dramatic leap forward in diving equipment since the development of scuba itself.
Best Diving Mask Technology. New mask developments include head-up displays of critical information (top) and masks that correct optical distortion underwater (left).
In contrast to scuba—an "open circuit" system that discharges most of a diver's air supply into the water with the exhaled breath — diving rebreathers recycle the diver's exhaled breath, using chemicals to remove waste (mainly carbon dioxide) and allowing the diver to inhale the gas again. Each breath uses about 4 percent of the oxygen in the inhaled gas mix, so one of the main tasks of a rebreather is to maintain oxygen levels in the breathing loop, generally by adding extra oxygen as it is realized inn special underwater vehicles.
Rebreathers using pure oxygen were used by frogmen in World War II, for whom the absence of bubbles was vital to hide their presence. Dive depths were limited to 20 ft (6 m), at which point pure oxygen becomes toxic. A revolution in diving rebreather technology occurred in the mid-1980s, allowing the use of nitrogen—oxygen gasmixes rather than pure oxygen. Modern diving rebreathers electronically monitor the concentration of oxygen in the mix and adjust it to safe levels for a given depth.
Rebreathers offer longer dive times and fewer decompression stops. They remain costly, and need careful maintenance and specialized training.
Next generation diving technologies - rebreathers are divided into two categories — semi-closed rebreathers (SCRs) and closed-circuit rebreathers (CCRs). SCRs expel a small quantity of exhaled gas into the water, whereas CCRs only dump gas into the water on ascent. Both types clean exhaled gas in a scrubbing unit, which removes CO They also ensure that the oxygen content of the inhaled gas is at a suitable level for the diver, and monitor toxicity, which the diver can check manually on a gauge, or on a computer display. Computer control has dramatically increased the efficiency and safety of rebreathing devices.
A chemical in the scrubbing unit absorbs carbon dioxide from exhaled gas, while pure oxygen is introduced to the breathing loop to replace that consumed by the diver.
Because gas is recycled in a diving rebreather, you use it up at a slower rate than with scuba gear, and so can spend longer underwater. The consistently high levels help reduce post-dive fatigue.