The origins of diving are firmly rooted in man’s need and desire to engage in maritime
commerce, to conduct salvage and military operations, and to expand the
frontiers of knowledge through exploration, research, and development.
Diving, as a profession, can be traced back more than 5,000 years. Early divers
confined their efforts to waters less than 100 feet deep, performing salvage work
and harvesting food, sponges, coral, and mother-of-pearl. A Greek historian,
Herodotus, recorded the story of a diver named Scyllis, who was employed by the
Persian King Xerxes to recover sunken treasure in the fifth century B.C.
From the earliest times, divers were active in military operations. Their missions
included cutting anchor cables to set enemy ships adrift, boring or punching holes
in the bottoms of ships, and building harbor defenses at home while attempting to
destroy those of the enemy abroad. Alexander the Great sent divers down to
remove obstacles in the harbor of the city of Tyre, in what is now Lebanon, which
he had taken under siege in 332 B.C.
Other early divers developed an active salvage industry centered around the major
shipping ports of the eastern Mediterranean. By the first century B.C., operations
in one area had become so well organized that a payment scale for salvage work
was established by law, acknowledging the fact that effort and risk increased with
depth. In 24 feet of water, the divers could claim a one-half share of all goods
recovered. In 12 feet of water, they were allowed a one-third share, and in 3 feet,
only a one-tenth share.
The most obvious and crucial step to broadening a diver’s capabilities
was providing an air supply that would permit him to stay underwater.
Hollow reeds or tubes extending to the surface allowed a diver to remain
submerged for an extended period, but he could accomplish little in the way of
useful work. Breathing tubes were employed in military operations, permitting an
undetected approach to an enemy stronghold (Figure 1-1).
At first glance, it seemed logical that a longer breathing tube was the only requirement
for extending a diver’s range. In fact, a number of early designs used leather
hoods with long flexible tubes supported at the surface by floats. There is no
record, however, that any of these devices were actually constructed or tested. The
result may well have been the drowning of the diver. At a depth of 3 feet, it is
nearly impossible to breathe through a tube using only the body’s natural respiratory
ability, as the weight of the water exerts a total force of almost 200 pounds on
the diver’s chest. This force increases steadily with depth and is one of the most
important factors in diving. Successful diving operations require that the pressure
be overcome or eliminated. Throughout history, imaginative devices were
designed to overcome this problem, many by some of the greatest minds of the
time. At first, the problem of pressure underwater was not fully understood and the
designs were impractical.
Figure 1-1. Early Impractical Breathing Device.
This 1511 design shows the diver’s head encased
in a leather bag with a breathing tube extending to
the surface.
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Figure 1-2. Assyrian Frieze (900 B.C.).
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An entire series of designs was based on the idea of a breathing
bag carried by the diver. An Assyrian frieze of the ninth century B.C. shows what
appear to be divers using inflated animal skins as air tanks. However, these men
were probably swimmers using skins for flotation. It would be impossible to
submerge while holding such an accessory (Figure 1-2).
A workable diving system may have made a brief appearance in the later Middle
Ages. In 1240, Roger Bacon made reference to “instruments whereby men can
walk on sea or river beds without danger to themselves.”
Between 1500 and 1800 the diving bell was developed, enabling
divers to remain underwater for hours rather than minutes. The diving bell is a
bell-shaped apparatus with the bottom open to the sea.
The first diving bells were large, strong tubs weighted to sink in a vertical position, trapping enough air to permit a diver to breathe for several hours. Later diving bells were suspended by a cable from the surface. They had no significant underwater maneuverability beyond that provided by moving the support ship. The diver could remain in the bell if positioned directly over his work, or could venture outside for short periods of time by holding his breath.
The first reference to an actual practical diving bell was made in 1531. For several
hundred years thereafter, rudimentary but effective bells were used with regularity.
In the 1680s, a Massachusetts-born adventurer named William Phipps modified
the diving bell technique by supplying his divers with air from a series of
weighted, inverted buckets as they attempted to recover treasure valued at
$200,000.
In 1690, the English astronomer Edmund Halley developed a diving bell in which
the atmosphere was replenished by sending weighted barrels of air down from the
surface (Figure 1-3). In an early demonstration of his system, he and four companions
remained at 60 feet in the Thames River for almost 1˝ hours. Nearly 26 years
later, Halley spent more than 4 hours at 66 feet using an improved version of his
bell.
Figure 1-3. Engraving of Halley’s
Diving Bell.
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With an increasing number of military and civilian wrecks
littering the shores of Great Britain each year, there was strong incentive to
develop a diving dress that would increase the efficiency of salvage operations.
In 1715, Englishman John Lethbridge developed a
one-man, completely enclosed diving dress (Figure 1-4). The Lethbridge equipment
was a reinforced, leather-covered barrel of air, equipped with a glass
porthole for viewing and two arm holes with watertight sleeves. Wearing this gear,
the occupant could accomplish useful work. This apparatus was lowered from a
ship and maneuvered in the same manner as a diving bell.
Lethbridge was quite successful with his invention and participated in salvaging a
number of European wrecks. In a letter to the editor of a popular magazine in
1749, the inventor noted that his normal operating depth was 10 fathoms (60 feet),with about 12 fathoms the maximum, and that he could remain underwater for 34
minutes.
Several designs similar to Lethbridge’s were used in succeeding years. However,
all had the same basic limitation as the diving bell—the diver had little freedom
because there was no practical way to continually supply him with air. A true technological
breakthrough occurred at the turn of the 19th century when a handoperated
pump capable of delivering air under pressure was developed.
Figure 1-4.Lethbridge’s Diving Suit.
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Several men produced a successful apparatus at
the same time. In 1823, two salvage operators, John and Charles Deane, patented
the basic design for a smoke apparatus that permitted firemen to move about in
burning buildings. By 1828, the apparatus evolved into Deane’s Patent Diving
Dress, consisting of a heavy suit for protection from the cold, a helmet with
viewing ports, and hose connections for delivering surface-supplied air. The
helmet rested on the diver’s shoulders, held in place by its own weight and straps
to a waist belt. Exhausted or surplus air passed out from under the edge of the
helmet and posed no problem as long as the diver was upright. If he fell, however,
the helmet could quickly fill with water. In 1836, the Deanes issued a diver’smanual, perhaps the first ever produced.
Credit for developing the first practical diving
dress has been given to Augustus Siebe. Siebe’s initial contribution to diving was a
modification of the Deane outfit. Siebe sealed the helmet to the dress at the collar
by using a short, waist-length waterproof suit and added an exhaust valve to the
system (Figure 1-5). Known as Siebe’s Improved Diving Dress, this apparatus is
the direct ancestor of the MK V standard deep-sea diving dress.
Figure 1-5. Siebe’s First
Enclosed Diving Dress and
Helmet.
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By 1840, several
types of diving dress were being used in actual
diving operations. At that time, a unit of the British
Royal Engineers was engaged in removing the remains
of the sunken warship, HMS Royal George.
The warship was fouling a major fleet anchorage
just outside Portsmouth, England. Colonel William
Pasley, the officer in charge, decided that his operation
was an ideal opportunity to formally test and
evaluate the various types of apparatus. Wary of
the Deane apparatus because of the possibility of
helmet flooding, he formally recommended that
the Siebe dress be adopted for future operations.
When Pasley’s project was completed, an official
government historian noted that “of the seasoned
divers, not a man escaped the repeated attacks of
rheumatism and cold.” The divers had been
working for 6 or 7 hours a day, much of it spent at
depths of 60 to 70 feet. Pasley and his men did not
realize the implications of the observation. What
appeared to be rheumatism was instead a symptom of a far more serious physiological
problem that, within a few years, was to become of great importance to thediving profession.
At the same time that a practical diving dress was being perfected,
inventors were working to improve the diving bell by increasing its size and
adding high-capacity air pumps that could deliver enough pressure to keep water
entirely out of the bell’s interior. The improved pumps soon led to the construction
of chambers large enough to permit several men to engage in dry work on the
bottom. This was particularly advantageous for projects such as excavating bridge
footings or constructing tunnel sections where long periods of work were required.
These dry chambers were known as caissons, a French word meaning “big boxes”
(Figure 1-6).
Caissons were designed to provide ready access from the surface. By using an air
lock, the pressure inside could be maintained while men or materials could be
passed in and out. The caisson was a major step in engineering technology and its
use grew quickly.
Figure 1-6. French Caisson. This
caisson could be floated over the
work site and lowered to the bottom
by flooding the side tanks.
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With the increasing use of caissons,
a new and unexplained malady began to affect the caisson workers. Upon
returning to the surface at the end of a shift, the divers frequently would be struck
by dizzy spells, breathing difficulties, or sharp pains in the joints or abdomen. The
sufferer usually recovered, but might never be completely free of some of the
symptoms. Caisson workers often noted that they felt better working on the job,
but wrongly attributed this to being more rested at the beginning of a shift.
As caisson work extended to larger projects and to greater operating pressures, the
physiological problems increased in number and severity. Fatalities occurred with
alarming frequency. The malady was called, logically enough, caisson disease.
However, workers on the Brooklyn Bridge project in New York gave the sickness
a more descriptive name that has remained—the “bends.”
Today the bends is the most well-known danger of diving. Although men had been
diving for thousands of years, few men had spent much time working under great
atmospheric pressure until the time of the caisson. Individuals such as Pasley, who
had experienced some aspect of the disease, were simply not prepared to look for
anything more involved than indigestion, rheumatism, or arthritis.
The actual cause of caisson disease was first
clinically described in 1878 by a French physiologist, Paul Bert. In studying the
effect of pressure on human physiology, Bert determined that breathing air under
pressure forced quantities of nitrogen into solution in the blood and tissues of thebody. As long as the pressure remained, the gas was held in solution. When thepressure was quickly released, as it was when a worker left the caisson, thenitrogen returned to a gaseous state too rapidly to pass out of the body in a natural
manner. Gas bubbles formed throughout the body, causing the wide range of
symptoms associated with the disease. Paralysis or death could occur if the flow of
blood to a vital organ was blocked by the bubbles.
Prevention and Treatment of Decompression Sickness
Bert recommended that
caisson workers gradually decompress and divers return to the surface slowly. His
studies led to an immediate improvement for the caisson workers when they
discovered their pain could be relieved by returning to the pressure of the caisson
as soon as the symptom appeared.
Within a few years, specially designed recompression chambers were being placed
at job sites to provide a more controlled situation for handling the bends. The pressure
in the chambers could be increased or decreased as needed for an individual
worker. One of the first successful uses of a recompression chamber was in 1879
during the construction of a subway tunnel under the Hudson River between NewYork and New Jersey. The recompression chamber markedly reduced the number
of serious cases and fatalities caused by the bends.
Bert’s recommendation that divers ascend gradually and steadily was not a
complete success, however; some divers continued to suffer from the bends. The
general thought at the time was that divers had reached the practical limits of the
art and that 120 feet was about as deep as anyone could work. This was because of
the repeated incidence of the bends and diver inefficiency beyond that depth.
Occasionally, divers would lose consciousness while working at 120 feet.
J.S. Haldane, an English physiologist, conducted experiments
with Royal Navy divers from 1905 to 1907. He determined that part of the
problem was due to the divers not adequately ventilating their helmets, causing
high levels of carbon dioxide to accumulate. To solve the problem, he established
a standard supply rate of flow (1.5 cubic feet of air per minute, measured at the
pressure of the diver). Pumps capable of maintaining the flow and ventilating the
helmet on a continuous basis were used.
Haldane also composed a set of diving tables that established a method of decompression
in stages. Though restudied and improved over the years, these tables
remain the basis of the accepted method for bringing a diver to the surface.
As a result of Haldane’s studies, the practical operating depth for air divers was
extended to slightly more than 200 feet. The limit was not imposed by physiological
factors, but by the capabilities of the hand-pumps available to provide the air
supply.
Divers soon were moving into
deeper water and another unexplained malady
began to appear. The diver would appear intoxicated,
sometimes feeling euphoric and frequently
losing judgment to the point of forgetting the dive’s
purpose. In the 1930s this “rapture of the deep” was
linked to nitrogen in the air breathed under higher
pressures. Known as nitrogen narcosis, this condition
occurred because nitrogen has anesthetic
properties that become progressively more severe
with increasing air pressure. To avoid the problem,
special breathing mixtures such as helium-oxygen
were developed for deep diving (see section 1-4,
Mixed-Gas Diving).
Numerous inventors, many
with little or no underwater experience, worked to
create an armored diving suit that would free the
diver from pressure problems (Figure 1-7). In an armored
suit, the diver could breathe air at normal
atmospheric pressure and descend to great depths
without any ill effects. The barrel diving suit, designed by John Lethbridge in 1715, had been an armored suit in essence, but one
with a limited operating depth.
The utility of most armored suits was questionable. They were too clumsy for the
diver to be able to accomplish much work and too complicated to provide protection
from extreme pressure. The maximum anticipated depth of the various suits
developed in the 1930s was 700 feet, but was never reached in actual diving. More
recent pursuits in the area of armored suits, now called one-atmosphere diving
suits, have demonstrated their capability for specialized underwater tasks to 2,000
feet of saltwater (fsw).
Figure 1-7. Armored
Diving Suit.
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By 1905, the Bureau of Construction and Repair
had designed the MK V Diving Helmet which seemed to address many of the
problems encountered in diving. This deep-sea outfit was designed for extensive,
rugged diving work and provided the diver maximum physical protection and
some maneuverability.
The 1905 MK V Diving Helmet had an elbow inlet with a safety valve that
allowed air to enter the helmet, but not to escape back up the umbilical if the air
supply were interrupted. Air was expelled from the helmet through an exhaust
valve on the right side, below the port. The exhaust valve was vented toward the
rear of the helmet to prevent escaping bubbles from interfering with the diver’s
field of vision.
By 1916, several improvements had been made to the helmet, including a rudimentary
communications system via a telephone cable and a regulating valve
operated by an interior push button. The regulating valve allowed some control of
the atmospheric pressure. A supplementary relief valve, known as the spitcock,
was added to the left side of the helmet. A safety catch was also incorporated to
keep the helmet attached to the breast plate. The exhaust valve and the communications
system were improved by 1927, and the weight of the helmet was
decreased to be more comfortable for the dive
After 1927, the MK V changed very little. It remained basically the same helmet
used in salvage operations of the USS S-51 and USS S-4 in the mid-1920s. With
its associated deep-sea dress and umbilical, the MK V was used for all submarine
rescue and salvage work undertaken in peacetime and practically all salvage work
undertaken during World War II. The MK V Diving Helmet was the standard U.S.
Navy diving equipment until succeeded by the MK 12 Surface-Supplied Diving
System (SSDS) in February 1980 (see Figure 1-8). The MK 12 was replaced by
the MK 21 in December 1993.
Figure 1-8. MK 12 and MK V.
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