page_title: History of underwater diving
section_title: The JIM suit
hierarchical_section_title: History of underwater diving / Atmospheric diving suits / The JIM suit
caption_attribution_description: A jim suit on display at the Royal Navy Submarine Museum
context_page_description: The history of underwater diving starts with freediving as a widespread means of hunting and gathering, both for food and other valuable resources such as pearls and coral, By classical Greek and Roman times commercial applications such as sponge diving and marine salvage were established, Military diving also has a long history, going back at least as far as the Peloponnesian War, with recreational and sporting applications being a recent development. Technological development in ambient pressure diving started with stone weights for fast descent. In the 16th and 17th centuries diving bells became functionally useful when a renewable supply of air could be provided to the diver at depth, and progressed to surface supplied diving helmets - in effect miniature diving bells covering the diver's head and supplied with compressed air by manually operated pumps - which were improved by attaching a waterproof suit to the helmet and in the early 19th century became the standard diving dress.
  Limitations in mobility of the surface supplied systems encouraged the development of both open circuit and closed circuit scuba in the 20th century, which allow the diver a much greater autonomy.
context_section_description: The Tritonia suit spent about 30 years in an engineering company's warehouse in Glasgow, where it was discovered, with Peress' help, by two partners in the British firm Underwater Marine Equipment, Mike Humphrey and Mike Borrow, in the mid-1960s. UMEL would later classify Peress' suit as the "A.D.S Type I", a designation system that would be continued by the company for later models. In 1969, Peress was asked to become a consultant to the new company created to develop the JIM suit, named in honour of the diver Jim Jarret.
  The Tritonia suit was upgraded into the first JIM suit, completed in November 1971. This suit underwent trials aboard HMS Reclaim in early 1972, and in 1976, the JIM suit set a record for the longest working dive below 490 feet (150 m), lasting five hours and 59 minutes at a depth of 905 feet (276 m). The first JIM suits were constructed from cast magnesium for its high strength-to-weight ratio and weighed approximately 1,100 pounds (500 kg) in air including the diver. They were 6 feet 6 inches (2.0 m) in height and had a maximum operating depth of 1,500 feet (460 m). The suit had a positive buoyancy of 15 to 50 pounds (6.8 to 22.7 kg). Ballast was attached to the suit's front and could be jettisoned from within, allowing the operator to ascend to the surface at approximately 100 feet (30 m) per minute. The suit also incorporated a communication link and a jettisonable umbilical connection. The original JIM suit had eight annular oil-supported universal joints, one in each shoulder and lower arm, and one at each hip and knee. The JIM operator received air through an oral/nasal mask that attached to a lung-powered scrubber that had a life-support duration of approximately 72 hours. Operations in arctic conditions with water temperatures of -1.7°C  for over 5 hours were successfully carried out using woolen thermal protection and neoprene boots. In 30°C water the suit was reported to be uncomfortably hot during heavy work.
  As technology improved and operational knowledge grew, Oceaneering upgraded their fleet of JIMs. The magnesium construction was replaced with glass-reinforced plastic (GRP) and the single joints with segmented ones, each allowing seven degrees of motion, and when added together giving the operator a very great range of motion. In addition, the four-port domed top of the suit was replaced by a transparent acrylic one that was taken from Wasp, this allowed the operator a much-improved field of vision. Trials were also carried out by the Ministry of Defence on a flying Jim suit powered from the surface through an umbilical cable. This resulted in a hybrid suit with the ability of working on the sea bed as well as mid water.
caption: A JIM suit on display at the Royal Navy Submarine Museum, Gosport
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