The Physics Of Scuba Diving: Swimming with the Fish

Have you ever wondered what it would be like to swim with the fish and
explore the underwater jungle that covers two-thirds of the earth\'s surface? I
have always been interested in water activities; swimming, diving and skiing,
and I felt that scuba was for me. My first dive took place while on a family
vacation. I came across a dive shop offering introductory dives, which
immediately caught my interest. After much convincing (my parents), with my
solemn assurance that I would be careful, I was allowed to participate in a dive.
I was ready, or so I thought. The slim basics such as breathing were explained
and I was literally tossed in. Sounds easy enough, right!, well WRONG!!. From
the moment I hit the water, my experience was much less than fun. I quickly
sank to the bottom into a new world, with unfamiliar dangers. I really wasn\'t
ready for this experience. I was disorientated, causing me to panic, which
shortened the length of my dive, not to mention my air supply. Let\'s just say I
would not do that again.

To start exploring the underwater world, one must first master a few
skills. Certification is the first step of learning to dive. From qualified
professionals one must learn how to use the equipment, safety precautions, and
the best places to dive. This paper is designed to help give a general
understanding of the sport and the importance that physics plays in it. Self-
contained Underwater Breathing Apparatus, or SCUBA for short, is a hell of a lot
of fun. However, there is considerably more to Diving than just putting on a
wetsuit and strapping some compressed air onto ones back. As I quickly learned,
diving safely requires quite a bit more in terms of time, effort, and
preparation. When one goes underwater, a diver is introduced to a new and
unfamiliar world, where many dangers exist, but can be avoided with proper
lessons and understanding. With this knowledge the water is ours to discover.

The Evolution of Scuba Diving

Divers have penetrated the oceans through the centuries for the purpose
of acquiring food, searching for treasure, carrying out military operations,
performing scientific research and exploration, and enjoying the aquatic
environment. Bachrach (1982) identified the following five principal periods in
the history of diving which are currently in use. Free (or breath-hold) diving,
bell diving, surface support or helmet (hard hat) diving, scuba diving, and,
saturation diving or atmospheric diving (Ketels, 4)


The development of self-contained underwater breathing apparatus
provided the free moving diver with a portable air supply which, although finite
in comparison with the unlimited air supply available to the helmet diver,
allowed for mobility. Scuba diving is the most frequently used mode in
recreational diving and, in various forms, is also widely used to perform
underwater work for military, scientific, and commercial purposes.

There were many steps in the development of a successful self-contained
underwater system. In 1808, Freiderich yon Drieberg invented a bellows-in-a-box
device that was worn on the diver\'s back and delivered compressed air from the
surface. This device, named Triton, did not actually work but served to suggest
that compressed air could be used in diving, an idea initially conceived of by
Halley in 1716. (Ketels, 9)

In 1865, two French inventors, Rouquayrol and Denayrouse, developed a
suit that they described as "self-contained." In fact, their suit was not self
contained but consisted of a helmet-using surface-supported system that had an
air reservoir that was carried on the diver\'s back and was sufficient to provide
one breathing cycle on demand. The demand valve regulator was used with surface
supply largely because tanks of adequate strength were not yet available to
handle air at high pressure. This system\'s demand valve, which was automatically
controlled, represented a major breakthrough because it permitted the diver to
have a breath of air when needed. The Rouquayrol and Denayrouse apparatus was
described with remarkable accuracy in Jules Verne\'s classic, Twenty Thousand
Leagues Under The Sea, which was written in 1869, only 4 years after the
inventors had made their device public (Ketels, 10).

Semi-Self-Contained Diving Suit

The demand valve played a critical part in the later development of one
form of scuba apparatus. In the 1920\'s, a French naval officer, Captain Yves Le
Prieur, began work on a self-contained air diving apparatus that resulted in
1926 in the award of a patent, shared with his countryman Fernez. This device
was a steel cylinder containing compressed air that was worn on the diver\'s back
and had an air hose connected to