immersion may be achieved on one unit. 
Amateur use of closed circuit scuba can be 
dangerous. The diver may be poisoned by faulty 
chemical filtering. He may suffer from anoxia 
or from oxygen poisoning. 
Use of closed circuit scuba in scientific 
diving is unnecessary since there is no need to 
extend submerged time or to conceal bubbles. 
Open circuit is recommended for scientific 
diving. The diver wears a high pressure air 
cylinder on his back. An automatic demand 
regulator mounted on the valve of the tank 
provides air through a hose to the mouthpiece or 
to the mask. The diver breathes air at ambient 
pressure. The exhaled air bubbles out into the 
water, hence the name open circuit. 
About an hour of submerged time is achieved 
with the most common size of scuba tank. This 
varies with depth and with the individual's 
respiratory rate. 
(Fig. 2 The Scuba Diver) 
Basic skindiving (breath holding diving) 
equipment is the mask, snorkel and fins. 
In addition to the basic equipment the 
scuba diver will need his breathing apparatus. 
He may also need a suit to protect him from cold, 
a weight belt, knife, compass, depth gauge, 
watch, and an inflatable flotation device. In 
some cases he might tow a surface float in which 
samples or tools can be carried. 
Many new pieces of accessory equipment are 
now available: 
Metal detectors, underwater prospecting 
and mining equipment, underwater lights, self- 
powered sleds and towing devices, small salvage 
equipment, underwater cameras, communication 
devices, diver sonar, and a host of others. 
(Fig. 3 Accessory Equipment) 
Scuba diving has to be experienced to be 
believed. The diver can hover almost effort- 
lessly over most scuba zone underwater locations 
while making continuous observations. He can 
rapidly change vantage points, pursue specimens, 
and handle objects. It is even possible to 
make notes or sketches, using special materials, 
underwater. 
Scuba is unparalleled for efficient 
shallow water search of an area. In fresh 
waters two divers on towed planes can cover a 
swath fifteen feet wide and mile long in less 
than a half hour. They will expend little 
energy compared to free divers. Using diving 
planes in depths to 40 feet, it is possible to 
double the air duration time of scuba. 
(Fig. 4 Use of Diving Planes) 
Unfortunately, most salt water areas do not 
lend themselves to the diving plane type of 
scuba search. The towed diver feels entirely 
too much like a trolled bait when in shark 
waters. 
Compare the diving ease of scuba with the 
difficulties of the traditional “hard hat” 
diver as he trudges slowly over the ocean floor 
in heavy gear, stirring up the mud. Ee is 
tethered to the surface by lines. A large boat 
or barge, a line tender, and usually a crew is 
necessary. His gear is expensive. He requires 
a great deal of training. 
(Fig. 5 "Hard Hat” Diver) 
These factors preclude the use of "hard hat" 
rigs by most scientists. He traditionally had 
an advantage over scuba divers. This was 
constant telephone communication with the 
surface which increased work efficiency and 
safety. Now the scuba diver can obtain under- 
water wire or wireless communications. 
The same inflexible rules regarding the 
physics and physiology of hard hat diving apply 
to the scuba diver. Proper training and 
adherence to the rules will minimize the danger 
of decompression sickness (bends), diving 
induced embolism, nitrogen narcosis, and other 
diving diseases. 
Before delving into the individual's 
physical and psychological ability to use scuba, 
let us compare scuba observation with other 
contemporary observation or sampling media. We 
must, of course, bear in mind that we are 
discussing only depths readily accessible to 
scuba divers. 
One type of observation medium is the 
reproduction of an underwater environment such 
as an aquarium. 
Let us begin by admitting that there is no 
completely satisfactory artificial environment 
in which to reproduce actual underwater condi- 
tions. Indeed, to make an authentic artificial 
reef of (for instance) underwater biological 
life would require that we reproduce conditions 
of current, depth, animal interdependence, and 
many other factors. 
A sampling medium such as trawling or 
dredging may bring up some undamaged marine 
specimens. This method gives scant information 
regarding the specimen's relationship to its 
environment. 
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