In 1930 Crozer joined the Royal Marines as a Boy Bugler age fourteen and a half. After his training he joined the Mediterranean Fleet in 1931 for two years. He then returned UK and was advanced from Boy to Adult service. In 1934 he returned to the Mediterranean Fleet until 1937. The next year he volunteered for Flying Training and on 6 March 1939 was transferred to the RN on probation as an Acting Leading Seaman to join No 3 Naval Pilots Course. Other Royal Marines on his course were; Lieutenants Hay and Parnell and Corporal Smart (the latter did not qualify). His Elementary Flying Training took place at Gravesend and Rochester before graduating to No 1 FTS at Netheravon on the 8 May. He completed his flying training course on 4 November 1939. The next day he was promoted to Acting Petty Officer Airman and immediately commenced seaplane training at RNASs Lee-on-Solent, Donibristle and Ford.

After qualifying as a Swordfish seaplane pilot his first experience was to operate from Portland conducting anti-submarine patrols in the Channel. However, in May 1940 Crozer was drafted to HMS Repulse, a Renown class battlecruiser, still flying Swordfish seaplanes. Repulse was engaged on covoy escort duties in the North Atlantic and up to Russia. She also went down into the South Atlantic and was involved in the hunt for the Bismarck, but without contact.

In August 1941,Repulse was fitted with a larger catapult and the aircrew converted to fly the amphibious Walrus. The Walrus was more capable of landing in heavy seas than the Swordfish seaplane and had an enclosed cockpit. Repulse sailed South escorting a convoy to South Africa and on to Columbo, where she was joined by the Prince of Wales, before they both arrived in Singapore on 2 December 1941. At this time, war had not been declared with Japan although the general feeling was that it would shortly break out. Two days later Repulse sailed for Darwin, Australia but on passage the news came through that the Japanese had attacked Pearl Harbor[Sic] and she returned to Singapore in time to witness the first Japanese air raids on the Island.

On the evening of 8 December 1941 both ships sailed with escorts as 'Force Z' to intercept reported Japanese landings on the East coasts of Malaya and Siam. The next day the Fleet was aware that it had been spotted by Japanese reconnaissance aircraft. At 9 am on 10 December 1941 Crozer's Walrus was launched to conduct a two and a half hour reconnaissance sortie of the Kuantan area with instructions to maintain radio silence and, on completion, be hoisted back onboard.  Crozer saw no evidence of a Japanese landing and it was not until 11 am that he saw one merchant ship, possibly towing other vessels, which he and his crew were unable to identify. He headed back towards Repulse in order to report their sighting by signal lamp but found both Repulseand Prince of Wales under heavy Japanese attack. He dived down to sea level realising as he did so that he was being fired at by one of the British escorting destroyers, which fortunately missed.  As he watched the Japanese aircraft attacking the two battleships it was very clear that he would not be able to recover to Repulse.  Therefore, Crozer decided to head for Singapore, although aware that he had insufficient fuel.

He ran out of fuel sixty miles short of Singapore and broke radio silence to report his position knowing that the position of the battleships had already been compromised, but not knowing they had been sunk. During the night, the destroyer HMS Stronghold found the aircraft and passed a tow rope. The Captain asked if they wished to sink the Walrus; Crozer declined. The tow commenced with Crozer and his crew remaining in the Walrus but the weather deteriorated and eventually they were taken onboard. When they arrived at the Naval Base they were delighted to find the Walrus was still attached to the tow rope. But meanwhile they had been posted missing presumed dead.

It was with a sense of relief to Crozer that HMS Exeter arrived in Singapore. She had lost one of her Walrus aircraft and, therefore, Crozer, his crew and their aircraft were embarked to take its place. Exeter sailed to escort evacuation convoys but on passage his aircraft was damaged by bomb blast whilst sitting on Exeter's catapult. He and his fellow Walrus pilot tossed up to see who would disembark with the damaged Walrus to Batavia where, shortly afterwards, he was transferred to a small merchant ship heading for Columbo. After Crozer had disembarked, Exeter  was sunk in the Java Sea and his fellow pilot, who thought he had had won the toss, became a Japanese prisoner of war for the rest of hostilities.

On arrival in Ceylon, Crozer was transferred back to flying a Swordfish dive bomber in defence of the Island. On Easter Sunday, 5 April 1942, his squadron was tasked to counter a major Japanese attack on Columbo. All the torpedo carrying Swordfish flying ahead of the dive bombers were shot down losing 70 per cent of their aircrew. Later that month, HMS Warspite arrived in Columbo short of an aircraft. Crozer, the only qualified Walrus pilot on the Island, embarked with a replacement aircraft. During the next two months Crozer disembarked to the Seychelles flying dawn and dusk reconnaissance flights and took part in the bombardment of Diego Suarez, Madagascar, on 6 May 1942 spotting the fall of shot and flying anti-submarine patrols.

On return to UK Crozer was posted to the 751 Squadron at the Observer Training School, RNAS, Dundee. He then moved to RNAS, Twatt, a satellite of RNAS, Hatston, and in May 1944, on one bizarre occasion, was flying a Miles Martinet when his observer, another Petty Officer, abandoned the aircraft by parachute “without permission” and was killed. Later in October of the same year Crozer was flying 712 Squadron Supermarine Sea Otters from RNAS, Hatston.

After the war, Crozer returned to Ceylon in 1946 once again flying the Walrus, but this time with 733 Squadron from RNAS Trincomalee. Subsequently, in 1948/49, he completed an exchange appointment at HMAS Albatross,with the RAN as a Warrant Flying Officer followed by appointments to RNASs Gosport and Culdrose and HMS Bulwark. Crozer enjoyed a long and fascinating career during which he flew the following aircraft; Swordfish, Walrus, Harvard, Moth, Sea Otter, Anson, Oxford, Sea Prince, Stinson Reliant, Percival Proctor and Miles Martinet. He retired from the RN on 23 June 1958 in the rank of Lieutenant (SD) (P) and transferred to the RNR as Lieutenant. On 23 June 1966 he was promoted to Lieutenant Commander RNR and six years later, on 3 July 1972, Crozer finally retired, 42 years after joining the Royal Marines as a Boy Bugler. He died in Portsmouth 7 December 2008 at the age of 93.