Born the younger son of Rev. Sir Clennel George Rivett-Carnac, 6th Baronet, Rivett-Carnac joined the Royal Navy in 1910 and served in World War I and was mentioned in despatches. He became Commander-in-Chief of the New Zealand Division in December 1938. He also served in World War II as Director of Training and Staff Duties at the Admiralty from April 1940 and as Commanding Officer of the battleship HMS "Rodney" from 1941 before becoming rear-admiral in charge of the Normandy beaches during the Allied invasion of Europe in 1944. In March 1945 he was appointed Rear-Admiral Q British Pacific Fleet until June 1945, then made acting Vice-Admiral with the new title of Vice-Admiral Q British Pacific Fleet he was responsible for organising logistical support of the BPF, including logistic activities ashore and for the ships of the Fleet Train until April 1946. He was mentioned in despatches twice during World War II. He retired in 1947.