This is an electronic reprint of an article that appeared in SOURCES
(Nov/Dec. 1991,p. 63-68; THE BEST OF SOURCES, p. 37-41). It has also appeared on numerous web sites and computer bulletin boards. This material is copyrighted and all rights are retained by the author. This material is made available as a service to the diving community by the author and may be distributed for any non-commercial or Not-For-Profit use.
There is an incredible fascination with diving on intact shipwrecks.
In the quest for this thrill of diving unmolested wrecks, some divers in the
Great Lakes are diving on compressed air in the vicinity of 200 Ft or
deeper. A few of these "sport divers" have taken years to develop skills,
technique and equipment that allow them to survive these penetrations into
that deep, dark, cold and silent world that lies beneath the sport diving
limit of 100 - 130 Ft. A few are truly highly skilled diving adventurers.
Some would call them pioneers. Others would call them something less
dignified. It is true that some walk with a noticeable limp, stand a little
funny (numbness in the legs), have difficulty remembering things or seem to
have somehow slowed their thinking and speech processes. None-the-less,
many of these diving adventurers have seen splendors that not many will ever
know. Other diving "adventurers" have found unique pains and death.
Divers new to our sport often do not realize that the successful deep
diver has generally taken a decade or more to develop the necessary skills,
equipment and technique to survive consistently this deeper diving. Make no
mistake, some of these divers are highly skilled and physically fit. That
exceptional proficiency, however, was not acquired in only a few days or
even years. Although most are self-taught, many of these deep divers were
trained when diving courses were longer and discussions on diving physics
and physiology were more extensive. Thus, they have had access to
information often missing in today's shorter curriculum... material that
is essential to make informed risk/benefit assessments. There are distinct
physiological problems associated with deep diving. Since divers do not
breathe water, the physiological impairments caused by deep diving can be
(and have been) life threatening. Sport "deep diving" courses are simply
insufficient training for diving to depths "below the limits." Divers
compelled to dive below 100 Ft should consider commercial or military dive
training - depths below 100 Ft are beyond the realm of sport diving...
Sport diving equipment and techniques no longer are adequate! In addition,
the training agencies will not, for a variety of reasons, address the
question of training for diving below 100-130 Ft.
There are those who earn their livelihood diving at depths below 100
feet. Many of these commercial divers would consider sport divers foolhardy
for diving under conditions a professional would consider to be too
dangerous. Note that commercial operations are conducted under federal/state
OSHA regulations. Recreational and scientific diving are specifically
exempted from these regulations. (Scientific diving, however, operates under
similar guidelines promulgated by the American Academy of Underwater
Sciences.) Whenever any employer/employee relationship exists, these rules
do apply. This means even if the diver is volunteering services and
equipment, non-recreational, non-scientific diving may be subject to
federal/state occupational safety regulations. These federal regulations
decree that all dives more than 130 Ft (some states have tougher
regulations; Michigan, for example, places the limit at 100 feet) or any
dive requiring decompression be conducted with a tender for each diver, a
stand-by safety diver, a surface decompression chamber on the dive site, and
an adequate supply of breathing gas for the diver, the stand-by diver and
the recompression chamber. The law specifies that the vessel used as a
diving platform be Coast Guard approved and commanded by a Coast Guard
licensed operator. The diving must be controlled by a designated "diving
supervisor" who must insure that all OSHA regulations are met during the
dive operation. There are additional requirements specifying the first aid
equipment, including oxygen, that must be on the dive site. The law also
requires that a complete time/event log be maintained. The British
government mandates that all diving more than 165 Ft under their
jurisdiction be done on mixed gas. In today's liability conscious society,
most legitimate diving contractors will exceed the minimum OSHA standards.
Since federal diving safety regulations prohibit non-recreational scuba
operations below 130 Ft, commercial/scientific diving is often a single
diver down mode with a tended tether, surface supplied breathing gas and
some sort of dry face mask/helmet equipped with hard wire communications.
This equipment significantly increases the safety of the diver. The
communication system allows the surface support personnel to monitor the
diver's psychological and physiological status. Surface control of the
entire dive operation minimizes task loading on the diver. This insures that
potential life threatening/saving decisions are made by narcosis free
surface support personnel. The dry mask/helmet provides mechanical and
thermal protection for the diver's head and face. More importantly, it
gives the diver a dry atmosphere that is breathable if a blackout occurs.
Commercial operations must be conducted with redundant equipment and
personnel. It is this contingency for the unexpected that increases diver
safety. This redundancy is most often missing in deep sport diving
excursions. (This equipment is beyond the finances and training of most in
the sport diving community.) Thus, the deep sport diving adventurer has very
little, if any, margin for human error.
There are significant physiological problems in deeper diving. These
Divers have been known to suddenly lose consciousness. This may be
from carbon dioxide toxicity, carbon monoxide poisoning, severe
decompression sickness, drowning (loss of regulator because of malfunction;
more likely a result of snag or hindered regulator exchange at depth;
vomiting from seasickness followed by aspiration of seawater, etc.),
hypoglycemia, hyperthermia, hypothermia, hypoxia from equipment malfunction
or miscalculation of breathing gas composition, severe nitrogen narcosis,
oxygen toxicity, pulmonary barotrauma of ascent (air embolism), or syncope
Each specific loss of consciousness under water may be due to a
unique combination of environmental, equipment or diver physiology factors.
It is not possible to predict each diver's vulnerability in absolute terms.
Conditions which may increase the likelihood of unconsciousness include:
low blood sugar, either from dieting or sustained workload, fatigue from
lack of rest or sustained workload, being too warm or too cold, dehydration,
drugs, particularly anything that has a warning label about "not operating
machinery," anxiety/fear and inexperience. Surveys have shown that the
inexperienced diver often is the most at risk. If a commercial/scientific
diver loses consciousness, he/she continues to breathe a dry gas inside the
mask/helmet; the lack of diver response alerts the surface communicator that
a problem has occurred. Often, the communicator is aware of a problem
before the diver and can initiate steps to alleviate the problem. Two-way
communication is a vital safety feature often missing in sport diving
situations. If a sport diver loses consciousness, there is concern that a
sport diver's regulator will fall out of the mouth. The sport diver then
attempts to breathe water and drowns. In addition, the unconscious diver
must depend on a buddy, if present, to insure return to the surface.
The cave diving community has noted a condition where the diver simply
appears to fall asleep. The eyes remain open; The diver does nothing but
breathe. In these cases, the regulator, for unknown reasons, has remained in
the mouth. The victims, rescued by their buddies, recall no warning signs.
In the 15 reported cases, all victims were on their deepest ever dive.
CARBON DIOXIDE (CO2) TOXICITY:
Carbon dioxide is the normal waste product of
human metabolism. As more work is done, more CO2 is generated. A person
in poor physical condition may generate 2-4 times the amount of CO2 as
someone who is in excellent physical condition while doing the same work
load. At depth, the density of the breathing gas increases. This increases
the work associated with breathing and may lead to inadequate pulmonary
ventilation. It is important for divers to realize that on scuba the CO2
comes from internal body chemistry, not from the gas being breathed. It is
the inability of the body to eliminate this waste product that creates the
problem. This means that CO2 can be a significant problem in deeper diving.
Symptoms of high CO2 usually begin with increased rate of respiration.
There is often the feeling that the regulator cannot supply enough air.
This may lead the diver to conclude falsely that an out-of-air emergency
exists. This feeling of inadequate respiration may be accompanied by a
feeling of constriction around the chest, heavy perspiration,
lightheadedness, or headache. The headache commonly is an intense pain in
the center of the forehead. This "CO2 hit," the feeling of total inadequacy
to breathe, can be a terrifying experience. Underwater "CO2 hits" can
easily lead to panic. Panic can lead to an uncontrolled "escape" to the
surface. This paniced ascent can cause a fatal cerebral air embolism. A
diver doing work at depth, however, may have little, if any, warning of CO2
problems before losing consciousness. Again, loss of consciousness under
water in sport diving equipment has a low probability of survival. In
addition, it is believed that high CO2 increases the likelihood of
decompression sickness, nitrogen narcosis and oxygen toxicity.
If the diver is aware that a CO2 problem is beginning to occur, the
diver should stop all activity and initiate slow, deep breathing until
perceived symptoms are eliminated. It is wise to continue resting a bit once
relief is felt and to proceed at a slower pace. Note that most experienced
divers develop a slow breathing pattern that means a routinely high CO2
level during diving activities. Work, coupled with poor physical condition,
aggravates the problem.
CARBON MONOXIDE (CO) TOXICITY:
Despite the tendency to blame diver
unconsciousness on this malady, it is rarely observed. Carbon monoxide is
primarily generated from incomplete combustion. It can be present in the air
supplied from faulty compressors (electric, as well as gas driven) or taken
into the compressor intake from a CO source such as a kerosine heater, gas
or diesel engine exhaust or cigarette smoke. The CO binds to hemoglobin
about 200 times tighter than oxygen. This means the hemoglobin that has
reacted with CO will not carry oxygen. Lack of oxygen can be fatal. The
uptake of CO is dependent on the concentration of CO in the breathing gas,
on respiration rate and the time of exposure. Symptoms may include: frontal
headache, nausea, tingling in the fingers and toes, lightheadedness, vision
disturbances or loss of consciousness with no warning. The often quoted
cherry red lips or fingernails are a very unreliable sign and may only be
visible at autopsy. At depth the increased partial pressure of oxygen may
mask some of the hypoxia created by the oxygen deprived carboxyhemoglobin.
On ascent, the hemoglobin will still be compromised, but the decreased pO2
will no longer compensate and unconsciousness occurs without warning.
Finally, the U.S. Navy pure air standards for breathing compressed air
allow only 20 ppm CO in scuba air. Smoke from an American cigarette
typically contains about 4% (20,000 ppm) CO. The average inhalation of a
smoker contains about 500 ppm CO. This means that finishing a cigarette
just before a dive will make about 3 -7% of the hemoglobin in the blood
unable to carry oxygen. The oxygen carrying capacity of the red blood cells
will be diminished for 5-8 hrs after the last exposure to smoke. Breathing
smoke, actively or passively, will decrease the ability of the blood to
carry oxygen and this decrease in efficiency may contribute to decreased
performance at depth.
The risk of permanent tissue injury increases with
depth. Many sport divers have been given the impression that "the bends" is
a benign disease. That simply is not true. The bends can kill, but most
often it cripples. The DAN numbers show more than 500 divers a year now
enter the chamber for treatment. After 3 months post treatment, 13% of those
treated still show some residual impairment. Severe sport diver bends hits
most often show spinal cord involvement. This means that anything "South"
of the lesion will be impaired. The spinal cord mediated functions most
often tainted are walking, urinating, defecating, and sexual response. So,
if you like to walk without a cane or wheelchair, go to the bathroom
unassisted or to have sex, it is worth your while to develop some
understanding of decompression sickness and its prevention. (A recent
national survey reported in Skin Diver magazine noted that approximately 60%
of those in the sport diving community surveyed could not recognize the
symptoms of the bends and almost every survey of divers done recently
suggests that more than 50% of sport divers cannot plan dives using
A real danger of decompression sickness is that it is often a
progressive disease; it may continue to get worse until treated. In North
America the time from onset of recognizable symptoms to chamber treatment is
often more than 12 hours. It is this delay that can be so devastating. It is
believed that the longer the delay between onset of severe symptoms and
treatment, the less the chance for total recovery. During the delay the
bubbles formed continue to impair or destroy body functions. The key to
successful recovery from the bends is immediate recognition of symptoms and
the prompt administration of the highest possible concentration of O2
(preferably by demand mask). Medical consultation/treatment should always be
sought. Not recognizing or ignoring the symptoms may allow the disease to do
more damage. Although there are anecdotal stories of acute relief of
decompression sickness symptoms without medical treatment, there is a
lingering question of the potential for long term damage even though
immediate clinical signs were absent or simply went away.
The problems linked to decompression sickness can primarily be called
"bubble trouble." Whenever bubbles form, they obstruct normal body function.
This may prevent normal exchange of nutrients and oxygen and allows waste
products to accumulate. This can, over time, create destruction of body
cells. Medical evidence is beginning to accumulate that suggests there may
be gradual deterioration of nervous system tissue upon repeated exposure to
deep diving. It is believed that this damage can occur without ever showing
gross clinical signs (ie. joint pain, etc.) classically associated with
decompression sickness hits. Although still far from complete, early studies
seem to imply that there is a marked deterioration in short-term memory and
reasoning skills in commercial divers aged 24-39. Autopsy studies of three
deep divers who died of non-diving related causes indicated that there was a
marked degradation of spinal cord tissue. It is believed that the spinal
cord lesions were created from diving. Although controversial, there is some
evidence that deep diving can block retinal blood flow and create vision
problems due to a damaged retina. Additional studies measuring blood
chemistry and urine of divers imply that the liver, as well, may be damaged
in divers diving as shallow as 30 meters (98 feet).
The body is a remarkable biochemical machine with much redundancy. It
can sustain some tissue damage that can be compensated for by this
redundancy. However, repeated exposure to tissue-damaging conditions will
ultimately result in loss of function.
The DAN numbers suggest that diving below 80 ft is a
significant risk factor for sport divers (more than 70% of DAN treatments
involved sport dives to depths below 80 ft). The deeper and more often this
deep diving occurs, the more the risk for long term neurological damage. It
is not possible to predict the type and severity of this physiological
Many sport divers consider the "high" associated with
narcosis to be a desirable event. This reflects a lack of understanding of
the dangers associated with breathing compressed air at depth. Nitrogen is
physiologically inert (not consumed in metabolism), but it does dissolve in
body tissues. As more and more nitrogen dissolves (Remember: Henry's Law),
the abundance of nitrogen interferes with the nervous system. The more
nitrogen present, the greater this loss of performance. The result is
impairment of intellectual capacity, degradation of neuromuscular
performance and changes in mood and behavior. The narcosis effect poses a
significant danger to the diver because as it increases the risk of an
accident due to inability to perform at depth, it decreases the diver's
perception that any problem may exist. Direct injury (aside from short term
memory loss) from narcosis is unlikely. The danger is people do not breathe
water. Under the influence of narcosis, divers may make inappropriate
decisions that place them at risk. (Such observed diver decisions have
included removal of life-support equipment at depth.) The degradation of
performance and perception caused by narcosis is often claimed to be the
primary reason for the sport diving limit of 100-130 Ft. (Historically,
however, this limit was considered by the US Navy as the maximum depth
that divers could do useful work while breathing from a two hose style
regulator (state-of-the-art at the time the limit was imposed.))
There is a marked variation in susceptibility to narcosis. This
variation is not predictable. Thus, it is not possible to equate absolutely
symptoms observed with depth. Some divers may be affected at 80 - 90 Ft or
even shallower. The effects may vary within the same diver from day to day.
The physiological degradation begins within moments of reaching depth and
increases with further descent. The higher mental functions such as ability
to reason - to make potential life-saving judgements, to remember recent
events, to learn new tasks and to focus concentration on a specific task are
first affected. (One reason for commercial hard wire communications is so
that surface personnel can monitor a diver's ability to function and remind
the diver what is to be done.) In warm, clear water divers may first feel
euphoric and overconfident... sort of like the "Do what you will, you can't
hurt me feeling" that arises from breathing nitrous oxide (laughing gas) at
the dentist's office. In cold, limited visibility water or in water where
neither the surface or the bottom is visible, the diver may develop a sense
of foreboding or impending doom. This sense of doom may escalate to terror
and panic. As depth increases, progressive impairment of both physical and
mental skills increases. The diver may feel drowsy. Idea fixation and
hallucination may occur. Some divers may note a narrowing of vision, like
looking through a narrow tube. It is common for a "narced" diver to forget
the reason for the dive. One reason that deep diving sport divers take
pictures is that often they can't remember what they saw on the dive. Short
term amnesia is a common aftereffect of narcosis. The photos (if
recognizable) tell them that they were at least somewhere near a wreck. The
severity of narcosis is aggravated by high CO2 levels, anxiety, cold,
fatigue and medications, particularly sedatives (anti-motion sickness
remedies?) and alcohol. There are anecdotal reports that women will show
shallower onset and increased severity of symptoms when diving during
periods of normal fluid retention.
Narcosis is easily avoided by liberal applications of common sense.
Simply confining dives to shallower than 90 Ft will most likely eliminate
most narcosis problems. Ascent when symptoms are recognized will relieve the
physiological compromises that narcosis generates. Relief is generally rapid
If you are human and dive below 90 Ft breathing compressed air,
then your normal human physiology will be impaired and it is impossible to
predict the severity of your inability to perform.
Oxygen is a component of the air we breathe. The body uses
chemical reactions based on oxygen to generate heat and chemical energy. It
is this process called metabolism that keeps us alive. Oxygen reacts
chemically with many different substances. The rate at which oxygen will
react (oxidation) with another chemical compound in the body is determined,
in part, by the partial pressure of the oxygen in the breathing gas mix. As
we descend in the water column, we increase the partial pressure of all
gases, including oxygen. Reactions with oxygen will therefore increase. Some
of these oxidation products can have harmful effects on human beings. The
exact mechanism of these harmful effects is not yet understood.
High oxygen concentrations affect the central nervous system in a
variety of ways. Observed symptoms, which may appear alone or in any
combination, include: nausea, vomiting, lightheadedness, dizziness that may
increase to vertigo, ringing in the ears, a feeling of impending collapse,
excessive perspiration, slowing of the heart rate, tunnel vision, muscle
twitching, particularly around the mouth and facial area, dilation of the
pupils, generalized peripheral muscle twitching, hiccups, amnesia,
hallucination and mental confusion. The symptoms can lead into a "grand mal"
epileptic-type seizure. This seizure may appear without warning. A grand mal
convulsive seizure at depth in sport diving equipment is not considered to
be a survivable event. Increased physical activity, excitement or anxiety,
and being too warm at depth appears to increase the risk of an oxygen
toxicity problem. The susceptibility of individual divers to oxygen
toxicity cannot be predicted. It is now believed to be dependent on the
individual's body chemistry on the actual day of diving. The once-used
"oxygen tolerance test" is no longer considered reliable.
It used to be believed that if the diver were breathing a gas
containing less than 2 ATA partial pressure of O2, that potential oxygen
toxicity problems would be eliminated. This corresponds to a depth of 33
Ft for breathing 100% O2. That is no longer current thinking. Current
practice is to avoid breathing gas that has a partial pressure of more than
1.8 ATA O2 (26 Ft on 100% O2; 249 Ft on air) with many diving authorities
wanting the pO2 limit to be lowered to 1.6 ATA (19 Ft on 100% O2; 218 Ft on
air) or to even a lower pO2. Oxygen toxicity seizures have been observed in
divers breathing compressed air in the 220 Ft range. This observation
suggests to avoid acute oxygen toxicity hits, dives on compressed air should
not exceed 180 Ft.
There are other problems that could result from the practice of
breathing pure O2 at depth (during decompression stops?). There are some
medical authorities who consider 100% O2 at elevated pressures a cellular
toxin. Breathing pure O2 at elevated pressures for extended times can
induce abnormalities in the red blood cells that carry O2 to the body. High
O2 concentrations can constrict blood vessels in the eye and lead to visual
problems. In addition, high O2 can create a mild hearing loss that may
appear hours after the dive and take a day or so to disappear. High pO2 has
also been proposed as contributing to dysbaric osteonecrosis ("bone death"-
usually seen in deep diving commercial divers; this malady may eventually
require surgery to replace bone joints with artificial devices.)
The potential for grand mal seizure and subsequent death
caused by oxygen toxicity makes diving below 180 Ft in sport diving
equipment on compressed air an extremely high risk activity. Below 200 Ft
many diving authorities believe that oxygen toxicity poses a greater risk to
the diver on compressed air than nitrogen narcosis.
SYNCOPE OF ASCENT:
This refers to the unexpected transient loss of
consciousness that may be due to partial breathholding during ascent. It is
believed to be caused by the expansion of gases within the thoracic cavity
that interferes with venous blood return. This lack of returning blood to
the heart reduces cardiac output. The reduced blood flow to the head causes
loss of consciousness. In sport diving equipment, this loss of consciousness
could lead to loss of regulator and subsequent drowning.
The effects of pressure on human physiology and
psychology are often unpredictable. Hyperbaric medicine is not yet an exact
science. Divers have been known to exhibit, for no known reason, behavior
that is contrary to survival. For example, I was with a diver along a sheer
rock wall at a depth of about 25 feet of water. We had been down for 18
minutes (following a 2 hr and 10 min surface interval from a wreck dive of
15 minutes in 40 F water at a maximum depth of 108 feet.) We exchanged
"time-to-turn-around-and-head-for-the-dive-boat" signals (a touch to the
watch and the "thumbs up") and the diver's "O.K." The diver then turned and
headed straight for the bottom. The diver was near 60 feet before I re-
established contact and asserted control. When I caught the diver, I grabbed
the shoulder and rotated the diver so that I could see the face. It was as
if I were waking the diver from a deep sleep. The diver, even when prompted
with eye-witnesses' accounts, has no recollection of the entire episode.
After several years, the event is still unexplained.
RISK: REAL OR THEORETICAL?
There is a wreck, the Gunilda, that lies at
256 Ft in the Great Lakes. Since it has historical significance and lies
close to the Canadian shore, the diving activity on this vessel has been
monitored. To date, there have been 26 divers who have visited this wreck.
Twelve of these divers (operating under commercial-type protocols) account
for 136 dives on this vessel. Within this group, 1 dive required treatment
for severe decompression sickness (to a diver who had 34 dives on this
wreck) and there were no fatalities. There have been 14 sport divers on
compressed air that have accounted for 33 dives. Of these 33 dives, 9 (27%)
have resulted in severe decompression sickness that required chamber
treatment, 5 dives (15%) were aborted due to severe narcosis that required
the diver to be rescued, and there were two fatalities (6%). In addition,
two of these surviving divers, one from each group, have subsequently died
on another deep wreck.
The population of sport divers who visited this wreck is small. These
divers have seen an awesome spectacle. Not all divers have been visibly
injured. However, there were two sport diving fatalities and a high
percentage of sport divers requiring treatment for severe decompression
sickness. It would appear from this admittedly small survey that diving to
250 Ft on compressed air does, indeed, pose a significant risk to the
It is most interesting to listen to these deep diving adventurers post-
treatment. One diver, after leaving the chamber against medical advice,
stated that he had experienced "no narcosis problem" at 256 Ft on compressed
air. (Remember, short-term amnesia is a common after effect.) This diver
went on to state that the bends had produced only a "mild" pain. (Perhaps
the "mildness" of the pain could be attributed to the morphine that was
administered to this diver by the emergency medical team on the flight to
No one has the right to restrict your personal style of
recreational diving. Lee Somers, Ph.D., Diving Safety Officer for the
University of Michigan and one of the Founding Fathers of our sport, calls
this "THE RIGHT TO DIvE!" Dan Orr, Training Co-ordinator for DAN, calls deep
sport diving "an exercise in natural selection." The decision to risk life
and spinal cord for the sake of recreational adventure rests with each
diver. This risk (loss of life or maybe only a slight compromise in mental
faculties, the ability to walk, go to the bathroom unassisted or to have
sex) / benefit (adventure, thrill, status, or fame) decision should,
however, be based on knowledge and evaluation of the actual risks incurred
and not solely on the perceived status of survival.
I once asked a very highly skilled and well known Great Lakes deep
sport diver about diving to extreme depths on compressed air without the
redundancy of commercial equipment and personnel. My question, "What do you
do alone at 250 Ft under the influence of narcosis to deal with an equipment
emergency?" His answer, "I die!" Enough said! The decision to dive to
"adventurer depths" rests with the individual diver. Choose wisely!
The author wishes to express his gratitude to Karl Huggins, Dan Orr
and Lee Somers for hours of stimulating conversation about this topic. In
particular, he would like to thank Karl for testing the capacity of his
answering machine with an impromptu discussion on the deep divers of the
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Saunders, Philadelphia, PA. 1990.
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Newsletter, Number 10, February-April, 1990, p. 1-3.
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7. Kindwall, E. & Cumming, J. "Decompression Survey Report", guest
feature in Bove, F. "Diving Medicine," Skin Diver, March, 1989.
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Sources, Sept/Oct, 1990, p. 48-51.
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Plenum Press, New York, NY. 1984.
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11. Somers, L. OCCUPATIONAL SAFETY AND HEALTH STANDARD FOR SCIENTIFIC
DIVING OPERATIONS, University Of Michigan, Ann Arbor, MI. 1990.
12. Somers, L. "The Right To DIvE", Unpublished Manuscript, 1990.
13. State Of Michigan Departments Of Public Health And Labor, "A
Standard For Diving Operations," Michigan State Department Of
Public Health, Lansing, MI. 1979.
14. U.S. Coast Guard, "Provisions For Commercial Diving Operations,"
Federal Register, 43, (222), November 16, 1978 as reproduced in
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DIVERS, Cornell Maritime Press, Centreville, MD. 1986.
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Federal Register, 50 (6), June, 1985, p. 1046-1050 as supplied by
About The Author:
Larry "Harris" Taylor, Ph.D. is a biochemist and scuba instructor at the University of Michigan.
He has authored more than 100 scuba related articles. His personal dive library (See Alert Diver,
Mar/Apr, 1997, p. 54) is considered by many as one of the best recreational sources of information
in North America.