For a brief period around 1910 Dawson worked for a commercial art studio in Bedford Row, London, but with the outbreak of the First World War he joined the Royal Navy.
Whilst serving with the Navy in Falmouth he met Charles Napier Hemy (1841–1917), who considerably influenced his work.
Dawson was present at the final surrender of the German High Seas Fleet and many of his illustrations depicting the event were published in The Sphere.
After the War, Dawson established himself as a professional marine artist, concentrating on historical subjects and portraits of deep-water sailing ships often in stiff breeze or on high seas.
By the 1930s he was considered one of the greatest living marine artists, whose patrons included two American Presidents, Dwight D Eisenhower and Lyndon B Johnson, as well as the British Royal Family.