Technology has the tendency to shake things up. And the diving industry is no different. One of the most monumental technological changes to rock the diving industry was the introduction of the dive computer. The dive computer catapulted the industry forward, removing the need for recreational divers to learn dive tables, making dive planning much easier and the act of diving itself much safer.
The First Line of Defense Against the Bends
Before dive computers became a standard addition to the scuba diving gear locker, there were dive tables. Also known as decompression tables, dive tables are charts that allow scuba divers to plan how much time they can spend diving at a specific depth without requiring a decompression stop. The purpose of a dive table is to calculate no-decompression time limits (NDL) so that divers may plan safe dive profiles and avoid getting decompression illness (DCI).
The first decompression tables were developed by Scottish physiologist John Scott Haldane in 1907. Haldane’s innovative experiments examined the effects of ambient pressure and nitrogen loading on goats and provided the first reliable insight into what happens to the human body when breathing in air under pressure. Before Haldane’s findings, in-depth (no pun intended) knowledge of the effects of ambient pressure at depth, nitrogen loading and decompression theory was shallow (pun still not intended). Many inventors and deep-sea divers perished because they dove to depths and under conditions that today we know to be unsafe, but of which they did not know the dangers.
When dive tables were created, they made diving much safer and more accessible to a wider range of people. Divers could estimate the amount of nitrogen their body would take on and the necessary surface interval between dives. Haldane’s tables were first adopted by the British and U.S. Navies and later by the major training and certification agencies when scuba diving became a popular recreational activity.
The PADI Recreational Dive Computer was based on the U.S. Navy tables, with slight modifications made to make them more conservative.
Over the years, it became apparent that there were some significant limitations to dive tables. One problem is that they rely on mathematical equations that are complicated and difficult to understand if you do not use them consistently. While every diver learns how to use them in their open water class, they are easily forgotten once the certification card is pocketed.
In his book Scuba Diving Explained, Lawrence Martin observed that “few recreational divers bother consulting any printed table when diving.” Printed in 1997, this quote rings even more true today. The advent of recreational scuba diving in the latter half of the 20th century further shifted divers’ reliance from dive tables to dive professionals. And when you aren’t planning the dive, you don’t really need to know about dive tables.
The Technological Revolution Comes to Diving
When the microprocessor began tearing up traditional industries in the ‘80s, the diving industry was not spared as even the relatively weak processing units of that time performed complex decompression calculations with ease. The first commercially available dive computer, the Orca EDGE, was released in 1983. While not the most advanced piece of technology, its release kicked off a slow but steady wave of advancement.
The old and the new. An Orca EDGE next to a Sheawater Perdix. Source: Shearwater
Here are four reasons why dive computer improved upon dive tables, eventually making tables obsolete for recreational divers:
1. Dive computers calculate NDLs dynamically and, therefore, more accurately.
Dive computers perform calculations in real-time based on your actual dive profile, not the abstract one you plot on a piece of paper. Dive tables assume a square-shaped profile where the diver descends to the maximum depth, stays there for the entire duration of the dive, and then ascends back to the surface. Nitrogen absorption levels are calculated accordingly.
This does not reflect the realities of scuba diving at all. Looking at digital dive logs plotted by modern dive computers, most recreational scuba dives profiles are not at all straight but rather erratic curves. Because dive computers continuously track depth and time and recalculate based on changing inputs, they take into consideration the changes in pressure and nitrogen loading that occur as a diver descends and ascends. As a result, dive computers provide a much more accurate estimate of the amount of nitrogen in the body, and therefore a more precise approximation of the no-decompression time (NDL). This allowing divers to take more time underwater while remaining within safe limits.
2. Dive computers reduce the risk of human error.
As with anything involving the human brain and mathematics, manual calculations based on dive tables are subject to human error. As scuba professor of Marine Science Alex Brylske pointed out in Dive Training magazine, “human error is so much a part of dive tables that several mistakes were inadvertently included in early versions of the U.S. Navy tables and not even recognized until they were recalculated decades later!”
Calculations for multilevel dives can be extremely complex and cumbersome to the layperson. One mistaken calculation can lead to an unsafe dive, possibly causing injury or death. While dive computers can fail due to mechanical problems or the battery dying, they do not make mistakes.
Dive computers have made dive planning and monitoring much easier for both recreational and technical dives.
3. Dive computers go above and beyond dive tables when it comes to safety.
Since the first dive computers were released in the 1980s, they have become extremely sophisticated in their functionality, especially as it relates to safety. In addition to dynamically tracking depth, dive time and NDLs based on a diver’s actual dive profile, dive computers will calculate decompression stop time and a ceiling depth for decompression stops should the diver exceed their NDL. Dive computers also keeps track of surface intervals between dives and takes into consideration residual nitrogen when conducting repetitive dives.
Dive computers also measure ascent rate. Ascending too fast from a dive can increase the risk of DCI, so knowing what is too fast is extremely useful safety feature. Dive tables are incapable of calculating a proper ascent rate because the rate changes based on a diver’s dive profile. Professor Brylske: “The admonition to ‘follow your slowest bubbles cannot compare to an ascent rate indicator as a safety device.”
4. Dive computers perform additional useful tasks.
The dive computers of today can do things that were simply unimaginable 20 or 30 years ago. Beyond safety calculations, dive computers have become extremely useful in making the dive experience easier and more efficient. By recording information such as time, depth and water temperature, dive computers make it easy to create dive logs with accurate information that divers can then learn from. Some include a social component which allows you to divers to transfer and share their dive data with friends, others have a built-in compass for navigation. More advanced computers even allow divers to track the remaining amount of gas in their cylinder or cylinders.
A Foregone Conclusion
While it may seem obvious now that dive computers would make the task of dive planning and tracking much easier, safer and more efficient, it was not always that way. When dive computers were first released they encountered opposition from many groups. Some were dead-set against bringing an electronic device underwater or relying on a computer to keep them safe in a dangerous situation. Others argued that an overreliance on computer technology would breed a new generation of lazy divers unaware of the fundamental principles of decompression that knowledge of dive tables entails.
To this day, there are those who swear by dive tables and most of the major certification agencies, including PADI, still teach them as part of the open water course. Nonetheless, dive computers are riding the waves of the inexorable march of progress. Pun totally intended.