JIM suit

The JIM suit is an atmospheric diving suit (ADS), which is designed to maintain an interior pressure of one atmosphere despite exterior pressures, eliminating the majority of physiological dangers associated with deep diving. Because there is no need for special gas mixtures, and there is no danger of nitrogen narcosis or decompression sickness (the 'bends'); the occupant does not need to decompress when returning to the surface. It was invented in 1969 by Mike Humphrey and Mike Borrow, partners in the English firm Underwater Marine Equipment Ltd (UMEL), assisted by Joseph Salim Peress, whose Tritonia diving suit acted as their main inspiration. The suit was named after Jim Jarrett, Peress' chief diver.

The petrochemical industry was unwilling to finance their research, but a grant was obtained from the British government, and a new company, DHB Construction (for Dennison, Hibberd and Borrow), was formed to develop the suit. The first JIM suit was completed in November 1971 and underwent initial trials aboard HMS Reclaim in early 1972. Two dives were conducted to depths in excess of 400 ft (121 m), and were limited only by the depth of the ambient divers providing support. Further development and testing continued until March 4, 1974, when Mike Humphrey conducted a chamber dive to the equivalent of 1,000 ft (300 m). The US Navy Experimental Diving Unit conducted tests in 1976.

In spite of the successful tests, the offshore petroleum industry still expressed little interest in the suit and it was not until 1975, when Oceaneering acquired DHB Construction and exclusive rights to the application of JIM suits in the oilfields, that the suit achieved success. This did not however please the British government, who after contributing money to the suit's development, did not want to see it being "given" to an American company over a British one. However, at the time, British diving concerns, most notably 2W, doubted the suit's abilities and therefore passed on purchasing the operating rights.

Its first commercial deployment was in 1974, when JIM suits were used in the recovery of lost oil tanker anchor chains in a Canary Islands harbor. In 1976 the JIM suit was used for a series of four dives on PanArtic's Hecla M25 well which were made through a hole cut in an ice floe 16 feet (5 m) thick, on which the rig was positioned, the first dive setting a record for the longest working dive below 490 feet (149 m), five hours and 59 minutes at a depth of 905 feet (275 m). In 1979, oceanographer Sylvia Earle set a human depth record of 1250 feet (381m) using a JIM suit.

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