Drawn to the ocean as a boy, Émile Cornellie was sent to Naval School while in military service and graduated as an officer. He served in various functions, on both marine and passenger vessels on the Oostende - Dover line. He also provided on board teaching for students of the Naval School on trips to Australia. In his spare time, he was known as a good sailor, racing since he had been allowed as a member to the Oostende Yacht Club in 1904 (which had required him to learn French first). He won numerous competitions, notably with his yacht “Flandria,” which had previously belonged to the Belgian crown prince.
During the First World War, Cornellie supported the Allied troops from the sea, and his Corps of Torpedo Boats and Marines played a part in the final Allied offensive of the war. When his corps was dissolved following the war, Cornellie tried to set up his own shipping company, but eventually became a naval consultant. In 1920, he competed in the Olympic sailing competitions that were held in his then-hometown, Oostende. Competing in the 6 metre class together with his son, Florimond Cornellie, he claimed first place. While only four boats competed, the 6 metre class was actually the best attended sailing competition at these Olympics.
Belgium