In World War II, Carlin was posted to the Indian Army Corps of Engineers, serving in India, Italy, and throughout the Middle East.

His mother, Charlotte Amelia Bramwell, died when he was four,[1] and he was raised by his father, Frederick Cecil Carlin, who was an electrical engineer employed with the Western Australian Government Railways.

[6] During the war, Carlin served in India, Iraq, Persia, Palestine, Syria, and Italy,[7] and by the conflict's end had been promoted to the rank of major.

After a considerable amount of trouble, the Carlins managed to purchase a 1942 Ford GPA (serial number 1239) from a government auction in Washington, D.C., for US$901 (equivalent to $12,294 in 2023).

[13] The construction of the under-belly fuel tank allowed it to be jettisoned when empty, reducing further its full weight of three long tons (6,720 lb or 3,048 kg).

[17] The craft was eventually landed five days after its departure, 40 miles (64 km) south of New York City near the Shark River Inlet in New Jersey.

[21][22] The Carlins set out for a fourth time in early August, and progressed further, being sighted several days after their launch by an American destroyer almost 200 miles (320 km) off of New York.

[24] Half-Safe and the Carlins were rescued approximately 270 miles (430 km) off New York by the oil tanker New Jersey, bound for Halifax, Nova Scotia.

[11] According to a message Carlin radioed from the tanker to his friends in New York, the couple "drifted and fished", enjoying a "pleasant life, cheaper than Atlantic City".

[26] At the time of the couple's rescue, he considered abandoning the entire voyage, but was convinced to continue by the tanker's Norwegian captain, who greeted Carlin with the words: "Hell, you're not going to leave that god-damned Jeep lying around?!

"[12] The Carlins' fourth failed attempt in two months led them to abandon the project for a period of time in order to raise more money.

With the New Jersey arriving in Halifax two weeks after their rescue, Carlin took up a position with a local marine salvage firm, while his wife returned to her family in Boston, and worked in a law office.

[12] When they struck a hurricane between the Azores and Madeira, and the superstructure looked like caving in, he got Elinore to recite the escape drill out loud in the tumult: "You shout 'OUT' – I get out and wait.

[37] From there, the Carlins drove through a number of European countries, where they engaged in sight-seeing before sailing across the English Channel and concluding the first part of their journey in Birmingham, where they arrived on 1 January 1952.

Throughout the journey from Nova Scotia to the Azores, both Carlin and his wife had suffered from severe hallucinations, including one instance where he had jerked awake to find himself 60° off course.

[31] Another important objective of their time in Britain was to repair Half-Safe, which had sustained large amounts of damage during the crossing, not least from Hurricane Charlie, which battered the vessel whilst it was amongst the islands of Macaronesia.

[11] The book was generally well received, with a reviewer in The Montreal Gazette describing Carlin as "an adventurer of the old school – full of the explorer's instinct, and with a dry wit that makes his story an odd mixture of high-adventure and real understatement".

[40] The Carlins then continued through Greece and Turkey, sailing across the Bosphorus to Asia Minor, before progressing through Syria, Jordan, Iraq, Iran, and Pakistan to Calcutta, India.

[12] Carlin later noted: "the 2000 miles across the Atlantic from Nova Scotia to the Azores were in many ways much less worrying than a similar distance covered on murderous roads in Persia".

[41] Half-Safe was returned to Calcutta on a steamship in January 1956; however, Elinore, Carlin's wife, left the trip in Australia, having tired of the long travel and the constant seasickness she was experiencing.

The two met on Burma's coast in late February 1956, and from there crossed the Arakan Yoma mountain ranges to the Irrawaddy River, where the vehicle was bogged down in mud for two days.

Upon his arrival in Hong Kong in early May 1956, Carlin was "mobbed by autograph-seeking girls", having been delayed on his voyage by engine trouble and headwinds in the South China Sea.

The craft sprang a leak while crossing the Tsugaru Strait, separating the southern island of Honshu from Hokkaidō, and collided with submerged rocks near the port of Muroran.

The craft was carrying enough fuel to last for approximately 21 days, but did not make contact within this time, causing the US Coast Guard's search and rescue station to be notified.

[50] Half-Safe landed on Shemya on 8 July, with the pair having made an unexpected detour to visit the town of Petropavlovsk on the Kamchatka Peninsula, at the time part of the Russian SFSR.

He would go on to write Once a Fool: From Tokyo to Alaska by Amphibious Jeep, a detailed account of his experiences with Carlin and Half-Safe, as well as becoming a prolific author on topics relating to Mesoamerica and East Asia, publishing over 100 books.

[3][58] After the conclusion of the trip, Half-Safe remained in the United States, where it was occasionally exhibited by Carlin's friend George Calimer, who was a co-owner of the vehicle.

[60] In 1999, the craft was transported by truck across Australia to Corowa, New South Wales, where it featured in an annual celebration on the Murray River, along with 16 other amphibious vehicles from the Second World War.