Saturation diving is one of the most talked-about subjects among dive watch enthusiasts and with good reason: many of the most interesting and technically advanced diver’s watches are specifically designed to suit the needs of professional saturation divers. And yet, it’s not often well understood by participants in the discussions what exactly saturation diving is, and how it differs from diving from, and returning to the surface (as scuba divers do).
Scuba involves suiting up topside, and descending to depth breathing some breathing gas mixture from compressed air tanks, and then returning to the surface. Deeper diving necessitates the use of an alternative to nitrogen and oxygen (which make up most of the air we breathe on the surface) as nitrogen can induce nitrogen narcosis at depths as shallow as 30 meters nitrogen narcosis is often likened to being drunk. For this reason in deeper diving helium and sometimes hydrogen are often used in combination with, or as a substitute for nitrogen; like nitrogen, helium is chemically inert but unlike nitrogen, it doesn’t cause narcosis at depth.
Scuba divers must generally make decompression stops on the way back up to the surface. The reason for this is that as you breathe compressed gasses, they gradually dissolve into your body tissues (you can avoid this by not diving deep enough, or staying down long enough, to require decompression stops, of course). Stopping occasionally on the way up, allows these dissolved gasses to leave the body gradually and harmlessly. If you come up without taking decompression stops, these same dissolved gasses will form bubbles in blood and body tissues, causing injury and even death (decompression sickness is also called “the bends”).
Saturation diving was developed and first used in the mid-1960s, for commercial diving. Commercial divers working on deeply submerged facilities (such as oil pumping equipment on the seafloor) need to stay down longer than the very limited time that scuba would allow at such depths, and also beyond a certain depth scuba becomes far too dangerous for regular commercial applications. To improve both bottom time and safety, saturation divers live and work from sealed pressurized chambers on surface support ships. Divers enter the chambers, which are then gradually brought to the pressure the divers will experience at working depth. The term “saturation” refers to the fact that the diver’s body tissues are saturated with the maximum amount of dissolved gasses possible at that depth.
To get to the seafloor, divers exit their pressure chamber habitat through an airlock, and enter a diving bell. The diving bell is then lowered to the seabed (or required working depth) and the divers exit the diving bell to work. A diver remains on board the diving bell to monitor the working divers. Once the divers have finished their shift, they re-enter the bell, which is hoisted back to the surface, and the next shift can begin. The advantages over scuba are considerable and while only a handful of scuba divers have ever gone deeper than 300m, saturation divers routinely work at depths of 100m to up to 500m.
Amazingly enough there appear to be few ill effects if any associated with working as a saturation diver (a few individuals seem susceptible to bone loss) and if done carefully, saturation diving is completely safe. However, the divers must remain in a pressurized environment for the duration of their work time, which can be as long as 3 weeks or more. This means living in a high-pressure habitat at very close quarters with other divers, under constant video surveillance (a necessity for safety reasons) with no privacy.
Considerable emotional balance is required and those with short tempers or poor teamwork skills need not apply. Food and other supplies must enter and exit the habitat via a small airlock and any carelessness in ensuring that the chamber is kept completely sealed would be fatal.
Imagine for instance that your working depth is 250 meters. That is equivalent to 25x the air pressure on the surface. Should an airlock fail, all that extra gas in a diver’s body will instantly look for the exits, leading to widespread immediate internal trauma and instant death. Major decompression accidents fortunately have historically been very rare.
Should a support ship suffer an emergency which necessitates abandoning ship, divers do have an exit strategy: an escape trunk leads from the on-board pressurized habitat to a pressurized (hyperbaric) escape module, allowing the divers to egress a stricken vessel safely.
The Rolex Sea-Dweller
The latest saturation diving watch from Rolex is the new-for-2017 Sea-Dweller ref. 126600. Read our Week On The Wrist coverage right here.
For watches, the problem is also internal pressure, in the form of helium. Oxygen forms molecules too large to penetrate the seals of a dive watch, but helium forms the smallest naturally occurring molecules, and can pass through the gaskets of a dive watch. This can lead to pressure building up inside the dive watch case. When divers begin decompression at the end of their multi-week working period, the drop in external pressure can lead to a relatively higher pressure inside the watch case as the helium cannot leave the interior of the case as quickly as external pressure is dropping (decompression time varies with working depth and can take anywhere from days to weeks). This can lead to the crystal being forced off when external pressure drops low enough.
There are two solutions. Many dive watch makers build helium release valves into the cases of their watches to allow egress of helium molecules in a controlled fashion during decompression. Simply unscrewing the crown might allow excess gas to escape in a violent fashion which could damage internal components. The other solution is to build a watch case that can’t be penetrated by significant amounts of helium to begin with; Seiko uses this approach for its Marinemaster Professional saturation diving watches although this seems to necessitate the construction of a somewhat larger case though the upside is greater structural integrity.
Finally there is the question of whether a date function is useful in a dive watch. It is arguable that a date is superfluous for a watch meant for scuba but it is hard to deny that it could be desirable for a saturation diver, who must live cut off from the outside world for weeks at a time.
It’s a highly stressful work environment although observation of correct procedures keeps things uneventful, catastrophe is only a mishandled valve away; something that surely weighs on every saturation diver’s mind. Anything that helps keep a diver oriented with respect to time would certainly be a plus under such circumstances.
With a total of 570 offshore drilling platforms in operation in the North Sea, Gulf of Mexico, and Southeast Asia alone as of 2015, there remains a great deal of work for saturation divers. Anecdotally, video documentary evidence would seem to indicate that not a few saturation divers wear purpose-built dive watches.
HODINKEE contributor and very experienced scuba diver Jason Heaton has views on helium escape valves; see what he has to say right here.