After his junior internship, MacInnis hoped to work with inventor and entrepreneur
Edwin Link in the field of deep diving, but had no idea how to reach him. In fall 1963 MacInnis placed a person-to-person telephone call to Link, who agreed to meet with him for fifteen minutes the next day at the
Navy Yard in
Washington, D.C. At the interview, Link offered MacInnis a position as the full-time doctor for his Man-In-Sea Project. In 1964, MacInnis became medical director of Man-In-Sea. The dive was successful, although MacInnis made a potentially grave error by placing a cover without a pressure-equalizing valve on a carbon dioxide-filtering device. In September 1967 MacInnis took part in a classified Ocean Systems mission aboard
Deep Diver on the
Grand Banks south of
Newfoundland. A cable plow, rumored to be used for burying a strategic communications cable, had been lost in 400 feet of water. Two Navy divers had already been killed trying to recover it. MacInnis was one of a crew of four Ocean Systems personnel who unsuccessfully attempted to recover the cable plow using the submersible. The mission was called off due to rising winds, and
Deep Diver was barely brought safely back aboard the
Canadian Coast Guard vessel
CCGS John Cabot. and in the search for the lost submarine
USS Scorpion. In late 1968 and early 1969, MacInnis took part in salvage operations after the crash of
Pan Am Flight 217 near
Caracas,
Venezuela. which was placed in
Georgian Bay near
Tobermory, Ontario, in June 1969.
Sublimnos had an "open hatch" policy, allowing access to any diver with a legitimate reason to use the habitat. In July 1969 MacInnis attended the
Apollo 11 launch at
Cape Kennedy, then traveled to Tobermory, where he dived to
Sublimnos and looked up through the water at the
Moon at the very moment the
astronauts were walking on it. == Arctic research ==