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by the author
Gary. L. Harris 

The organization that is now known as the Naval Experimental Diving Unit (NEDU) had its beginnings at the old Washington Navy yard in 1927. During the early decades of the 20th Century, due to several high profile submarine disasters, and accompanying loss of life, it became painfully obvious to the United States Navy that its diving equipment and training were inadequate to the needs of a modern, emerging, global military force. For example, when the US submarine S-51 collided with the steamer "City of Rome" and sank with most hands off Block Island in 1925, the Navy discovered that it had only a handful of competent deep-sea divers, and most of these were not certified to dive below 50 feet (15.2 meters)!

However, despite financial and political limitations on its mission, the early Navy diving unit successfully added to and provided revisions to decades of the US Navyís Diving Manual, promoted mixed-gas (Helium/Oxygen) diving procedures and made invaluable technical enhancements to submarine escape and rescue.

The naval yard diving organization went through a series of restructures and name changes in its early years. In 1945 it was commissioned as the Navy Countermeasures Station. Then in 1955 it became the Mine Defense Laboratory. It was as the Mine Defense lab that the USN Decompression Tables were finally standardized. It was also this organization that began the now famous Genesis Project (1963) and the Sealab-I habitat experiments of the early 1960s. Genesis was the worlds first saturation diving studies, and Sealab-I was the American Navyís first open water saturation diving experiment in which divers worked and lived in a bottom sitting habitat at 193 feet depth (58.5 m) for 11 days.

The Mine Defense Laboratory became the Naval Ship and Development Laboratory and went on to create the successful Sealab-II habitat and the ill-fated Sealab-III which was supposed to saturate a crew of divers to 600 feet (182.8 m) , but was canceled in 1968 after one of the divers lost his life in an underwater accident.

Finally in 1972 the Naval Ship Development Laboratory became the Naval Coastal Systems Laboratory with its future was intimately linked to underwater military and life support research. The Washington based NEDU had depth limitations to 1000 feet (305 meters) of sea water and its wet pot (a water filled pressure chamber) could only maintain water temperatures in the range of about 70 degrees Fahrenheit (32 C). Such simulation conditions were simply unrealistic given the arduous, cold, deep conditions divers had to contend with.

The 1960s saw a virtual explosion of primarily American space and undersea related research and innovation. This undersea research came about due to the US Navyís Dr. George F. Bondís discovery of saturation diving techniques and the civilian commercial diving sectors pursuit of offshore oil (among other reasons). For example, the 1960ís saw the invention of Joe Savoieís modern light-weight diving helmet, Westinghouse and Taylor Divingís first lock-out diving bell and heli-ox push-pull diving systems. By the late 1960s civilian, oil-patch commercial diving companies were planning 1500 foot (457 m) mixed-gas dives and instead of investing in vulnerable, inefficient bottom sitting habitats (like Sealab), the civilian contractors were building deck mounted saturation systems with attached lock-out diving bells (Personnel Transfer Capsules).

However, by the early 1970s, federal funding for military undersea related research had virtually dried up, or so it appeared. Consequently the US Navy found itself falling behind the civilian commercial diving industry in technical innovation, a disparity it has still not closed in some areas. But naval divers were also up against obstacles other than lack of overt congressional funding. During the 1960s American nuclear submarines became capable of diving well below 1000 feet (305 m). Naval planners scrambled to keep up with submarine crew rescue to such depths. However, unknown until recently another factor began to drive American naval diving research in the late 1960ís and 1970s: Cold War espionage.

While funding for overt naval diving research dried up, covert funds were diverted to one of the most startling intelligence gathering operations ever undertaken. An undersea espionage project called "Ivy Bells." American naval deep-sea divers and submarine crews literally tapped the Soviet (Russian) Navyís undersea phone lines. With the publication of the book "Blind Manís Bluff" it has come to light that during the dark days of the Cold War the US and its allies desperately needed information on the intentions of the Soviet Navy, especially the locations of their nuclear missile firing submarines. It occurred to an American naval officer in the middle 1960ís, who was working in Naval Intelligence, that the Russian Navy bases in the sea of Okhotsk and bases at Petropavlovsk-Vladivostok might be linked to the mainland by undersea phone cables.

The US sent the small, aging submarine "Halibut," equipped with a diver lock-out chamber, to investigate this possibility. The Halibut could lock-out divers to a depth of 600 feet (182.2 m). While at 400 feet (122 m) depth the Halibutís divers managed to attach an undersea listening mechanism to the 5 inch (127 mm) diameter Russian subsea phone cables. At first the dive crews left listening devices on the phone cables every few months; coming back at intervals to download recordings of what the Russians thought were confidential military conversations. Then, by the late 1970s, a device was built that could be left on the Russian cables for more than a year. Information garnered from these phone taps, which went on for almost 20 years, some have said, helped prevent WW-III.

While the morality and risk to peace of such military diving operations can be debated, the courage of the naval divers and submariners who pulled off this enormous intelligence coup canít. If the crews had been discovered they would have lost their lives or, at best, been imprisoned in a Russian Gulag for decades. The US Navy has never made public the type of diving gear used by these naval divers. Obviously at 400 to 600 foot depth heli-ox and saturation diving gear would have been needed. Also, gear that could protect deep divers from the numbing cold in northern Russian Waters was required.

Though no one has publicly said, it stands to reason that the Navyís Experimental Diving Unit was involved at some level in these operations. The NEDU certainly continues to pursue a great deal of closed and semi-closed rebreather and cold water diving research. If one looks back at some of the diving equipment developed for the US Navy in the 1960s by Kirby-Morgan and Morse Diving Company, certainly some of it appears to have attributes for clandestine uses. I doubt that anyone at these two firms had any inkling of what their experimental gear may have been used for, however, in the absence of hard data, this is just idle speculation. The undersea phone taps were quietly discontinued after an American traitor, Ronald Pelton, a national Security Agency employee, told the Russian about the project in the 1980s. This turncoat received a mere $35,000 for this information from the Russians.

By 1972 the US Navy had completed its Ocean Simulation Facility (OSF), and it and the NEDU were relocated in 1975 to Panama City, a small tourist town in the Florida Panhandle. The OSF is essentially the core of a complex of interrelated research facilities managed by the Naval Sea Systems Command. With five interconnected dry and wet chambers, for a total volume of 3,300 square feet (306.5 square meters), the huge OSF is in fact one of the worldís largest hyperbaric wet pots. It is essentially a huge chamber with openable domes on each end. It can contain 55,000 gallons (203,500 liters) of water at any desired salinity. The OSF is capable of pressurization down to 2,250 feet (686 m) of sea water equivalent, or an altitude equivalent of 150,000 feet (45,720 m), and it can test men or machines. In fact the OSF is large enough to sail a miniature submarine inside.

In addition to being filled with salt or fresh water, the OSF can be set up to operate at tropical temperatures of 90 degrees Fahrenheit (32.2 C) or arctic temperatures as cold as 34 degrees F (1.1 C). Because of the cold temperatures and extreme pressure stresses, the OSF and its plumbing had to be built to the same standards as nuclear submarine containment vessels.

The NEDU has contributed to far more than just diver life support or covert military operations. Its contributions also include research in naval salvage diving, submarine rescue and support, inshore warfare, acoustic countermeasures, mine and ordinance disposal and countermeasures, navigation and even amphibious operations. Over its lifetime NEDU scientist, engineers and divers have helped to develop underwater specialized and hydraulic tools, hull scrubbing equipment for naval vessels and ship husbandry and a myriad of other diver related support gear. They, and their civilian contractors have also developed the various, unusual diving helmets seen on these pages.

Facilities at the NEDU complex include unmanned test facilities, test pools, environmental chambers, cardiopulmonary laboratory, gas analysis laboratory, specimen analysis laboratory, technical library, biomedical research facilities, and a class 100,000 clean room (for cleaning of oxygen piping, etc.,). Various other systems also are present for testing and evaluation of diving systems, such as flow capability of diving helmets, communication equipment, hyperbaric life support systems and one-atmospheric (ADS) diving suits.

In this time of the war on terror, the NEDU continues to be a pivotal facility enhancing American and allied warfighting capability and providing equipment that can strengthen intelligence gathering capabilities. The NEDU is nothing less than a "Force Multiplier" in and of itself. Presently its staff of 160 highly qualified engineers and divers are represented by almost every underwater arm of the US Navy, such as SEALS (sea-air-land), EOD (Explosive Ordnance Disposal), SEEBEE (naval construction) and UMO (Undersea Medical Officer), fleet salvage and even other branches of the armed forces, such as the US Army. The NEDU has a good website that gives more detail at:

Continue to part 2 to see some great experimental diving helmets