becoming uncomfortable and possibly even painful as the diver continues to
descend. This sensation is the result of a squeeze on the air spaces. A
squeeze is not only a scuba phenomena but may also be experienced in a swimmers
ears when diving to the bottom of a swimming pool. A squeeze, then is a
pressure imbalance resulting in a pain or discomfort in a bodies air space. In
this situation, the imbalance is such that the pressure outside the air space is
greater than the pressure inside (Ketels, 76-77).
Squeezes are possible in several places: ears, sinuses, teeth, lungs and
ones mask. Fortunately, divers can easily avoid all these squeezes.
To avoid discomfort, pressure inside an air space must always equal the
water pressure outside the air spaces. This is accomplished by adding air to
the air spaces during descent, before discomfort occurs. This is called
equalization.
Compared to the ear and sinus air spaces, the lungs are large and
flexible. As a scuba diver, one automatically equalizes the pressure in the
lungs by continuously breathing from the scuba equipment. When you skin dive,
holding ones breath, the lungs can be compressed with no consequence as long as
they are filled with air when one begins to descent. The lungs will be reduced
in volume during decent and will re-expand during ascent to nearly the original
volume when one reaches the surface (some of the air from the lungs is used to
equalize the other body air spaces) (Ketels, 78).
In a healthy diver, blocking the nose and attempting to gently blow
through it with the mouth closed will direct air into the ear and sinus air
spaces. Swallowing and wiggling the jaw from side to side may be an effective
equalization technique. Some divers even attempt a combination of the previous
two methods.
As mentioned previously along with squeezes, the lungs experience no
harmful effects from the changes in pressure when holding ones breath while skin
diving. At the start of the skin dive, one takes a breath and descends; the
increasing water pressure compresses the air in the lungs. During ascent, the
air re-expands so that when reaching the surface, the lungs return to their
original volume (Ketels, 78).
When scuba diving, however, the situation is different. Scuba equipment
allows one to breathe under water by automatically delivering the air at a
pressure equal to the surrounding water pressure. This means the lungs will be
at their normal volume while at depth, full of air that will expand on ascent
(Cramer, 51).
If a diver breaths normally, keeping the airway to you lungs open, the
expanding air escapes during ascent and your lungs remain at their normal volume.
But, by holding ones breath and then blocking the airway while ascending the
lungs would over expand, much like the sealed bag. Expanding air can cause lung
over-pressurization (lung rupture), the most serious injury that can occur to a
diver. The most important rule in scuba diving is to breath continuously and
never hold your Breath. Lung rupture will occur unless pressure is continuously
equalized by breathing normally at all times (Cramer, 52).
Other physical Phenomena’s
As an air-breathing creature, we have evolved to live on land. Above
the water, we see, hear and move about in a familiar and comfortable manner that
seems normal because we have adapted to an air environment.
Under water, though, one enters a new world, where seeing, hearing,
staying warm and moving are different. This is because water is 800 times more
dense than air, affecting light, sound and heat in ways that we aren’t used to.
Sight seeing is a big part of what diving is all about. One dives for
numerous reasons. A primary purpose is to see new environments, aquatic life
and natural phenomena. Since underwater sight seeing is important, like buying
a new camera, one must learn, how. Therefor when diving, one must know how the
liquid environment affects vision.
To see clearly under water, a mask is needed because the human eye
cannot focus without any air space in front of it. A mask provides the air space.
Without the mask, you can see large objects, but they will be blurred and
indistinct because your eyes cannot bring the rays of light into sharp focus.
Only by wearing a mask can you see sharply (Ascher, 9).
Light travels at a different speed in water than in air. When light
enters the air in your mask from the water, the change in speed causes its angle
of travel to shift slightly. This causes a magnificent effect that makes
objects under water appear 25% larger and closer (Ascher, 52).
Water has other effects on light. As you descend, there is less light.
This is due to several facts: some light reflects off the water’s surface, some
is scattered by particles in the water, and some is absorbed by the water itself.
However, water does not absorb light uniformly.
White light, such as sunlight, is actually composed of various colors
mixed together. The colors are absorbed one by one as depth increases: First
red, followed by orange and yellow. Since each color is part of the total light
entering the water, less light remains as depth increases and each color is
absorbed. For these reason, deeper water is darker and less colorful. To see
true colors, divers sometimes carry underwater lights with them (Resneck, 151).
Underwater Hearing
The underwater world is not a silent world. One can hear many new and
interesting sounds, like snapping shrimp, grunting fish, and boat engines
passing in the distance. Since sound travels farther in water than in air, one
is able to hear things over much longer distances.
Sound also travels about four times faster in water than in air and
because of this, one may have trouble determining the direction a sound is
coming from (Cramer, 95).
Speech is virtually impossible under water because ones vocal cords do
not work in a liquid environment, not to mention the addition of the tube in
ones mouth. Communication by sound is usually limited to attracting the
attention of another diver by rapping on the tank with a solid object, such as a
knife. The diver will hear the rapping, but may not be able to tell where the
sound is coming from.
Heat loss in water.
Diving stops being enjoyable when the diver gets cold. In fact, even a
small loss of body heat has the potential to be a serious health threat. For
these reasons, understanding about heat loss is important.
In air, body heat is lost as it rises from the skin into the air, as it
is carried away by air currents, or as perspiration cools the skin through
evaporation. Water conducts heat away from your body twenty times faster than
air does, meaning that for a given temperature, water has a far greater cooling
effect. Even seemingly warm 86F water can become chilly after a while (Cramer,
91).
The loss of body heat in water can quickly lead to a serious condition
unless you use insulation to reduce the heat loss. Insulation through the use
of exposure suits is recommended for diving in water 75F or colder. Just as one
dresses according to the temperature and conditions to go outdoors, one must
dress appropriately for diving.
Motion in water
One of the best aspects of diving is that it can be so relaxing.
There’s little reason for hurrying. By learning how to move without
breathlessness, cramping or fatigue, you learn to relax during a dive.
Due to the greater density of water, resistance to movement in water is
much greater than in air. If you’ve ever tried to run waist-deep water, you’ve
experienced this. In overcoming this increased resistance while diving, the
best way to conserve energy is to move slowly and steadily. Avoid rapid and
jerky movements that waste energy. Simply take your time. After all this is a
sport to enjoy.
Conclusion
Several months after my vacation, I decided to give scuba diving a
second chance. However, this time I decided to do it right. I signed up to
take a P.A.D.I. certification, which is one of the many internationally
recognized scuba associations. It was here, in a properly structured course,
consisting of both theoretical and practical (in water) sessions where I was
properly re-introduced to the sport.
Since my introductory dive from hell, I have had the chance to become
quite the scuba enthusiast. Partaking in numerous dives not only in warmer
climates (preferably) but in the colder Montreal waters as well, scuba diving
has become part of my lifestyle. I participate in and enjoy every opportunity to
re-visit the underwater world that once scared me away.
In this paper, I included some history of the evolution of the sport in
order to point out that there is more to this particular sport than jumping into
the water. Scuba is a complex sport and can not be enjoyed without some
scientific knowledge. Scuba diving did not simply evolve, but it is the result
of numerous inventions and physical properties. One could only imagine the
difficulty that those historic divers (scientists) had in creating this sport.
My objective in writing this paper was not to deter people away from the
sport, but to stress the importance of the knowledge that is required to
properly and safely partake in it. Like everything else in life, one must work
towards a goal, and this is no different. One will quickly see that the payoff
is far greater than anything else ever experienced. Recreational scuba is meant
to be a very enjoyable and relaxing sport. The scenery is magnificent and the
sensations are truly indescribable.
Today, scuba diving is quickly becoming one of the expanding trades.
Whether for military, research, business, or recreation, hundreds of thousands
of people are heading for the depths, to experience the unknown. My advice for
a new diver is to do it right. Get the proper certification and make each dive
a safe one.
When a diver is fully trained, and in good mental and physical condition,
safe diving can be one of the most enjoyable of experiences. The true beauty of
the underwater world, coupled with the marvelous almost-weightlessness of
floating with neutral buoyancy is an indescribable experience.
Bibliography/Further Reading
Ascher, Scott M. Scuba Handbook for Humans. Iowa : Kendall/Hunt Publishing
Company. 1975.
Cramer, John L. Ph.D. Skin and Scuba Diving: Scientific Principles and
Techniques. N.Y.: Bergwall Productions, Inc. 1975.
Ketels, Henry & McDowell, Jack. Safe Skin and Scuba Diving, adventure in the
underwater world. Canada : Little, Brown and Company (Canada) Ltd. 1975.
Koelzer, William. Scuba Diving, How to get started. Pennsylvania :Chilton Book
Company. 1976.
Resneck, John Jr. Scuba, Safe and Simple. New Jersey : Prentice-Hall, Inc. 1975.
Tillman, Albert A. Skin and Scuba Diving. Iowa : Wm. C. Brown Company Publishers.
1966.