Maxwell's first boat came in the form of a Turkish dongola left over from a London exhibition. At 20 years of age, Maxwell rigged it with sail, leeboards and sailed it to Charing Cross and back. The boat was known as "the Junk".

Shortly after 1901, at the behest of the Swiss Modern Languages instructor at the Manor House School, Maxwell journeyed to Switzerland and built a boat to sail home. He wrote of this adventure in The Log of the Griffin, his first book. With the loss of Griffin in 1903 during an attempt to cross to Holland, Maxwell purchased his next, slightly larger boat, Walrus. He bought Walrus in Holland and wrote of his adventures in A Cruise Across Europe published in book form in 1906 (originally, like many of his writings at this time, coming out in serial form in The Treasury magazine).

Maxwell was known amongst his friends as something of a "mad" artist in his youth—in the friendliest sense of course. He had a reputation for single-mindedness when it came to getting the sketch—regardless of rain, present company's comfort, etc.

In 1907 Maxwell married Fanny Eveline Marie Morgan (known as Eva). Practical-minded Eva offered a sound counter-balance to Maxwell's chaos. Herbert Knight, a close friend, who described Maxwell as follows (using the nickname "Malcolm"):

"Now Malcolm has personality transcending the normal as a hundred to one. He recognises the dramatic limitations of speech; to him it is an obscure text requiring physical illustration. He jerks his arms, wags his head, hops and jumps about regardless of everything save a genuine desire to make himself understood. He is a delightful, cheery fellow, with a robust appreciation of the joie de vivre."

Waterloo Bridge to Limehouse, The Yachting Monthly, July, 1910

Knight would write of the young Maxwell pair and some of their adventures in The Little Affair of the Thames and Medway Canal. It was shortly after this that Maxwell built his next boat, Penguin, based on the hull of a Thames tugboat (which features prominently in Knight's "Waterloo Bridge" story). He outfitted her as a floating studio on whose decks he could arrange large canvases for painting. Penguin was the married couple's first home—even their wedding reception was held aboard.

His pre-war interest in both sketching maritime scenes and exploration by boat led to a commission as the Naval Artist for The Graphic (a relationship that would last through the coming war) and, after the articles by Knight a few years earlier, resulted in a number of accounts of his adventures afloat, documented for in The Yachting Monthly. These included A Motor Boat's Discovery of the Upper Medway, The Cruise of the Penguin, and A Voyage to the Vosges. His adventures nearly always included a man named "Brown" who was sometimes his friend Walter Henry Brown but who was occasionally also his younger brother Gordon—renamed "Brown" for the occasion.

As with so many of his contemporaries—including brother Gordon—when war broke out in 1914 Maxwell volunteered. Initially he spent a year working as a correspondent for The Graphic at the front, illustrating all he saw. After a year he enlisted as a Lieutenant in the R.N.V.R. and was posted to the command of a Motor Launch (M.L. 139) stationed on the North Sea Patrol and out of Sheerness. He continued to provide illustrations and paintings to The Graphic and The Yachting Monthly. In accordance with regulations and tradition his work was all published without his usual signature. Instead it was simply signed "A Naval Officer". Indeed, many in the "regular" Navy were unaware of his ongoing illustration work.

Some mention of his progress in the Navy can be found within the Gazette where his promotion within the R.N.V.R. from Sub-Lieutenant to temporary Lieutenant is noted on 18 July, 1916—at the same time as the same promotion for fellow sailor Edwin S. Turner:

R.N.V.R.
To be tempy. Lieut. -
Tempy. Sub-Lieut. Digby E. Easton. 17th July 1916.

The undermentioned tempy. Sub-Lieuts. to be tempy. Lieuts.: -
Edwin S. Turner. 6th Apr. 1916.
Thomas Sinclair. 17th June 1916.
Donald Maxwell. 24th June 1916.
William Robinson. 26th June 1916.

Eventually, his contributions to The Yachting Monthly were noticed by the Admiralty and his identity revealed which led to a 1918 transfer to duty as an official Admiralty War Artist in the Mediteranean and Palistine—a posting he arrived at just as the war ended. This was an area of the Empire he'd already had some experience with during a previous visit in 1912. He wrote of his experiences during the war in The Last Crusade, 1914–1918. He also provided numerous illustrations for brother Gordon's The Motor Launch Patrol and The Naval Front documenting the part they'd played during the war as part of the Auxiliary Patrol.

After the war it was time to recover Penguin from the saltings where she was laid-up in order to set off on a new adventure. Maxwell intended to take her from the Port of Rochester all the way to the Alps in something of a race against his friend, Oswald Short (the famed sea-plane designer). The entire family was to accompany him. However, after an auspicious start, Penguin encountered stiff seas and heavy winds and was nearly lost due to a loose lee-board. She had to be towed into Ramsgate. This adventure was recounted in The Yachting Monthly along with an article in The Graphic as well.

For years before, and certainly after the war Maxwell was a churchwarden at St. Matthew's Church, Borstal in which town he based his family.

"St Matthew's has become well-known for the story behind the seven Sanctuary Lamps. In 1912 one of the churchwardens, Donald Maxwell, visited Syria and made for Damascus. Here he found the "Street called Straight", where once stood the house to which Saul was taken after being blinded in his conversion experience on the Damascus Road. In this street, Donald Maxwell came upon the workshop of an old Arab brass-worker. He admired some lamps being fashioned by the old man so much that he ordered a set to take home to his own Parish Church, promising to call back for them at a later date. The intervention of World War I prevented this, and the Arab was pressed into service by the conquering Turks to make munitions for them.

Maxwell was back in the area in 1920 and, out of curiosity, again made his way to the "Street called Straight". To his astonishment the old Arab was still there and explained that despite everything the lamps had been made and buried throughout the war under the floor of his house. He was a Christian and, knowing the destination of the lamps, refused to take anything for them. They were brought home to Borstal and on the day of the Feast of St Paul were dedicated by the Bishop.

The lamps were originally lit by oil, but were later electrified due to the fire risk. Apart from the central lamp they appear to be in pairs, but in fact the hand-working of each one is different, and - perhaps unique in a Christian church - each incorporates in its design the Moslem Star and Crescent, but surmounted by the Christian cross."

History of St. Matthew's

Known Boats:

• "The Junk"—an un-named Turkish-style small boat. A "dongola".
• Griffin
• Penguin—a converted Thames tug heavily modified by Maxwell with assistance from Sparkes of Limehouse
• Walrus
• Dolphin