Coontz graduated from the Naval Academy in 1885, and served at the Navy Department and in several ships over the next decade, among them vessels stationed in Alaskan waters and the Great Lakes.

[3] Following further duty afloat and ashore, Coontz, then a lieutenant commander, was executive officer of the battleship USS Nebraska during the 1907–1909 world cruise of the "Great White Fleet".

Coontz had just been assigned to the Pacific Fleet in September 1919, when he was selected to become Chief of Naval Operations (CNO), succeeding Admiral William S. Benson.

While dealing with these problems, Admiral Coontz established a unified United States Fleet and strengthened the CNO's position within the Navy Department.

Relieved as CNO in August 1923, by Admiral Edward W. Eberle, Coontz was able to return to sea as Commander in Chief of the United States Fleet.

In June 1925, as Admiral, the Coontz led U.S. fleet, consisting of 57 vessels of United States Navy carrying about 25,000 officers and crew, departed the port of San Francisco, California.

This was the first massed deployment of American battleships since the "Great White Fleet" cruise, nearly two decades earlier, and a valuable demonstration of their strategic reach.

After retiring, Coontz wrote a memoir chronicling his early life growing up in Hannibal, Missouri, and his navy career, titled From the Mississippi to the Sea.