Early home movies show a young Johnson training for a life at sea, climbing a telephone pole in his backyard, and wrestling to prepare for the inevitable fights he believed would occur due to his reading the novels of Jack London and Joseph Conrad.
Johnson became a professional sailor (joining the Merchant Marine in 1926) working summers as crew and captain of various yachts including the "Charmian" for Newcomb Carlton (President of Western Union.), which led to the opportunity to sail on the Peking. He was an amateur filmmaker and his footage on the barquePeking in 1929 would become the now famous film Around Cape Horn.
While serving as mate on board the Wanderbird, Johnson met (Harriet) Electa "Exy" Search whom he married in 1933. The Johnsons circumnavigated the world seven times on two vessels, both named Yankee, each trip with a new crew and each taking approximately 18 months. The first Yankee, bought in 1933, was a Dutch North Sea pilot schooner.  The second Yankee, bought in 1947, was a retired German North Sea pilot schooner which the Johnsons rerigged as a brigantine.  They then retired from circumnavigation and, in 1958-9, had the last Yankee built at Westhaven in Zaandam, Holland. She was a steel ketch for sailing the inland waterways of Europe, designed by Irving Johnson and Olin Stephens of Sparkman & Stephens. 
Many of the Johnsons' voyages have been documented in their own books and many articles and videos produced by the National Geographic Society and others throughout their sailing career. With an amateur crew, they traveled hundreds of thousands of miles to the islands of the South Pacific, ports of call in Southeast Asia, around the Cape of Good Hope and home to Gloucester without incident 18 months later seven times.
Upon the urging of Bill Donovan, then head of the predecessor to the OSS, Johnson joined the U.S. Navy, and was at Pearl Harbor on the day of the attack. His intimate knowledge of the South Pacific made him a natural choice to advise the Pacific Fleet on the tides, swells, currents, depths and shoals around the treacherous reefs and atolls of the South Seas. He was commissioned a Lieutenant Commander, and joined the USS Sumner, finishing the war as her commanding officer. On board they created and printed five color charts, scouted out potential harbours for US Navy vessels, and conducted underwater demolition to improve the suitability of some of the harbours. Johnson also dove on recently sunken Japanese vessels, searching for classified Japanese documents. One success was a chart of the minefields surrounding Japanese harbors.