4 April 2003

Established in 1927, the Navy Experimental Diving Unit completed 75

years of pioneering diving and hyperbaric

research in 2002. Among NEDU’s accomplishments over the past three quarters of

a century are ground-breaking work developing standard decompression tables

for air diving, helium-oxygen diving procedures, recompression treatment tables,

surface decompression procedures, saturation diving, early sea-floor habitats, diver

thermal protection, and submarine rescue.

Experimental diving began in the

Navy in 1912 at the Brooklyn Navy Yard

under the direction of Chief Warrant Officer George D. Stillson. His small group

developed the first standard Navy diving

equipment, tested Dr. John S. Haldane’s

theories on staged decompression, and

extended the maximum diving depth of

U.S. Navy divers from 60 to nearly 300

feet.

Navy diving stagnated immediately

after World War I with the closing of the

Diving School in Newport, Rhodes Island,

but experiments with helium were conducted in cooperation with the Bureau of

Mines in the mid-twenties.

The Navy Experimental Diving Unit

was formally established in 1927 at the

Washington Navy Yard adjacent to the reestablished Diving School.

NEDU’s early focus was on submarine rescue and experiments with helium

diving. In the mid-1930s, Doctors C. W.

Schilling, A. R. Behnke, and O. E. Van der

Aue, became the first medical staff at

NEDU. Their early experiments demonstrated the usefulness of oxygen for treating decompression sickness and proved

conclusively that breathing high-pressure

air caused physical and mental performance decrements. They also developed

surface decompression procedures for

submarine rescue.

The first operational use of helium

was during the salvage of the USS

SQUALUS, which sank in 243 feet of water

off the Isle of Shoals near Portsmouth,

NH. Equipment and procedures developed at NEDU, including the McCann

Rescue Chamber, were essential to the rescue of the 33 crewmen who survived the

initial sinking.

During World War II, NEDU began

work on early oxygen rebreathers, investigated oxygen toxicity, and tested captured

enemy diving equipment. The unit also

tested breathing systems and pressure

suits for aviators and investigated altitude

bends, a new phenomenon observed with

the advent of high performance, high altitude aircraft.

In the 1950s, NEDU developed surface decompression tables using oxygen

for air diving. In 1956, NEDU developed

procedures for air diving that became the

basis of the Standard Air Decompression

tables, the Surface Decompression Using

Air table, and the Repetitive Air Dive

tables. These air tables became the standard worldwide.

In the early 1960s, CAPT George

Bond, Medical Corps, began the first early

experiments in saturation diving, Project

Genesis, at the Submarine Medical Research Laboratory in Groton, Connecticut.

He and his team of aquanauts conducted

their first manned saturation dive, Genesis

D, to 100 fsw at NEDU in the spring of

1963.

Saturation diving progressed dramatically through the 1960s and 1970s. New

diving records were set and broken, including the first 600 fsw dive in 1964, the

first 1,000 fsw dive in 1968 in a joint venture with Duke University, and a 1,600 fsw

dive in 1973 at Taylor Diving and Salvage

in New Orleans LA, which was then the

world’s largest hyperbaric facility. In the

1960s, NEDU developed recompression

treatments that would become known as

(NEDU continued on page 5)

By: LCDR Marc Tranchemotagne

HT1/SEAL Dan Jakobs (SDVT-2) testing the new KMS-48 mask in conjunction with the MK25.
A p r i l 2 0 0 3 5

Treatment Tables 5 and 6, still in use today.

In 1975, NEDU relocated from the

Washington Navy Yard to its present location on the Florida panhandle in Panama

City. It was commissioned as a shore

command under Naval Sea Systems Command. The new unit included the Ocean

Simulation Facility—the largest manned

hyperbaric facility in the world—and the

Experimental Diving Facility for unmanned

testing.

Through the 1970s and 1980s, NEDU

tested a great variety of diving equipment

and achieved new records for depth and

duration in saturation diving. Among the

equipment tested was the MK 12 Surface

Supplied Diving System (SSDS), which replaced the MK V that George Stillson had

tested in the 1920s, and which would be

replaced by the MK 21/Superlight 17, also

tested at NEDU.

During the 1980s and 1990s, NEDU

did a large amount of saturation diving to

evaluate diving equipment, examine deep

saturation diver thermal protection problems, test active and passive diver thermal

protection, validate decompression algorithms, test various carbon dioxide

absorbents and scrubber systems, develop Treatment Table 7, and conduct mission-specific training for various special

projects.

In 1998, the diving biomedical research and development functions from

the Naval Medical Research Institute (NMRI)

in Bethesda, MD, were

consolidated with

NEDU.

From 1999 to 2002,

NEDU conducted two

warm water diving studies to address concerns

of the Naval Special

Warfare community regarding critical gaps in

the Navy’s knowledge

of warm water diving

physiology.

In 2001 and 2002,

NEDU divers made essential contributions

to the ex-USS MONITOR salvage project.

The mission was a three-year, joint National Oceanographic and Atmospheric

Administration and U.S.

Navy expedition to recover artifacts from the

historic site 16 miles

south-southeast of

Cape Hatteras Lighthouse off the North

Carolina Coast.

 In 2002, NEDU completed the final openwater demonstration

dives for certification of

the MK 16 Mod 1 UBA

to 300 feet of seawater

(fsw) in the Gulf of

Mexico. The 300 foot

open-water certification

dives completed a fouryear product improvement process that included: extending the

working limit from 200 to 300 fsw, developing 1.3 atmosphere constant partial pressure of oxygen decompression tables for

nitrogen (N2

O2) and helium (HeO2) diving,

providing an HeO2 repetitive dive capability for dives shallower than 200 fsw, testing an emergency breathing system (EBS)

with integral communications, adding an

integral buoyancy compensation device,

and adopting an improved full face mask.

Over the past 75 years, NEDU has

evolved from a small team of Navy divers

to a diverse workforce of over 150 people

including military divers from the Fleet,

EOD, SEABEE, and SEAL diving communities; PhD scientists and engineers; diving medical officers, physiologists, and research psychologists; and many talented

technicians and support personnel.

NEDU’s mission has evolved from Gunner

Stillson’s original assignment to evaluate

diving equipment and procedures to a

much broader mandate that includes a

wide range of undersea and hyperbaric

biomedical research and development. As

NEDU looks towards the immediate future,

we foresee research focused on procedures for contaminated water diving, advances in diver thermal protection, furthering our understanding of oxygen toxicity and decompression illnesses, and

preserving a Navy capability for saturation

diving.

The author wishes to acknowledge

that much of the information on NEDU’s

early history was taken from a 50-year retrospective written by LT R. C. Carter, MSC,

USN and published in the Fall 1977 Faceplate, “NEDU celebrates 50th Anniversary

1927-1977,” and as NEDU Report 1-77,

“Pioneering Inner Space: The Navy Experimental Diving Unit’s First 50 Years.”

LCDR Marc Tranchemotagne is currently

Executive Officer at the Navy Experimental

Diving Unit.

(NEDU continued from page 4)

Ocean Simulation Facility, 55,000 gallon wet pot.

ENCS/DSW Vern Geyman, SM1/DSW Jorge Guillen, DC1/DV

Jeremy Mullis, HT1/DV Bart Washburn decompressing during

USS MONITOR diving operations.