George “Johnny” Johnson was the last survivor of the British Royal Air Force “Dambusters” who used specially designed bouncing bombs to breach German dams and flood German weapons factories during World War II.

In a heavy Lancaster bomber flown by the American pilot Joseph C. McCarthy, and flying only 60 feet above reservoirs in the Ruhr Basin, Mr. Johnson was what the RAF called the “bomb-aimer,” or bombardier, on one of the most daring military actions of the war, a major morale booster for British and Allied forces.

Mr. Johnson, 101, died on Wednesday in a care home in Bristol, England. His death was reported by Britain’s national news agency, the Press Association, citing his family. The cause was not immediately available. His death was also announced on Twitter by Carol Vorderman, a TV presenter and family friend who had campaigned for years for Mr. Johnson to be awarded a knighthood.

Mr. Johnson served with the RAF’s celebrated 617 Squadron and was a sergeant at the time of the “Dambuster” raid — Operation Chastise — which began before dawn on May 17, 1943.

A total of 19 bombers took part, using cylindrical 8,500-pound bombs that would hop along the surface of the reservoirs the way children skip flat stones across a creek. Bouncing along the water, the bombs evaded underwater German anti-torpedo nets before detonating against the dams.

The Dambusters lost eight of their 19 Lancasters to German antiaircraft fire during the raids, with 53 crewmen killed and three captured as prisoners of war. Mr. Johnson recalled that when he and his crew returned to base, RAF waitresses, who knew all the crew members by name, wept when they served him breakfast amid the empty chairs of his comrades.

As bomb-aimer on the Lancaster called T-Tommy, Mr. Johnson lay on his stomach in his tiny compartment beneath the cockpit manned by McCarthy, a Long Islander who had joined the Canadian Air Force to help Britain before the U.S. entered the war. Through a Perspex screen, Mr. Johnson said he felt as though he was surfing across the reservoirs at breathtaking speed as McCarthy approached their target, the Sorpe Dam.

McCarthy was in charge of the bomber, but when to release the bomb was Mr. Johnson’s call. And it had to be at the perfect moment — the perfect height, angle and speed.

Only after nine approaches, and after being cursed at with dark humor by his crew mates, did he release the bomb. By the light of the moon, he saw it bounce toward the Sorpe Dam. McCarthy had to pull up sharply to avoid the dam by only 30 feet.

“In the totally clear moonlight, it was an incredible sight; after nine dummy runs, we were satisfied we were on the right track,” the Times of London quoted Mr. Johnson as saying years later. “I pushed the button and called, ‘Bomb gone!’”

His caution, he said he realized, was “an easy way to become the most unpopular man [in the plane] in double-quick time.”

“But there was no point in not doing the job properly,” Mr. Johnson said.

As McCarthy avoided heavy antiaircraft fire, Mr. Johnson could see millions of gallons of water shooting up into the sky, some of it falling on the Lancaster and drenching the exposed rear gunner.

McCarthy got the Lancaster back to an RAF base at Scampton, Lincolnshire, not far from Mr. Johnson’s birthplace, despite a wing and a wheel having been shot up.

On their return, Mr. Johnson and his crew were told that their bomb did not fully breach the dam but had caused enough damage to flood the surrounding area, where Nazi munitions factories were set back by months, according to historians. It later emerged that other Lancasters had totally breached two other dams, the Eder and the Möhne, destroying factories, bridges and other infrastructure vital to the Nazi war effort.

Thousands of German troops were pulled out of the front lines along the river Rhine to repair the damage. More than 1,000 civilians were also killed by the floods. The victims included many German farmers, as well as Russian and other prisoners of war who had been forced by the Nazis to work on the dams, fields or factories.

Some Britons, in the immediate aftermath of the raids and in later decades, questioned whether the operation had been worthwhile, given the RAF casualties and the civilian losses on the ground. For the rest of his life, Mr. Johnson described these critics as “retrospective historians.”

“I felt the raid was successful,” the Times of London quoted him as saying. “It proved to Hitler and the Nazi hierarchy that what they thought was indestructible the RAF could get through and destroy.”

Furthermore, he said, “it did delay, not as long as we would have liked it to do, but it did delay some of his armament production … He had to bring in skilled workmen from other war work elsewhere to repair those dams.”

But most important, he said, was “the morale effect” upon the people of Britain.

The story of the air raids was told in one of Britain’s best-known postwar movies, “The Dam Busters” (1955), starring Richard Todd and Michael Redgrave. Film director Peter Jackson — director of “The Lord of the Rings” — is said to have bought the rights to make a new version, partly based on Johnson’s 2014 autobiography, “The Last British Dambuster.”

“The Dambusters’ March” is one of the most popular military marches in Britain, played at many war memorial services.

George Leonard Johnson, the youngest of six children, was born Nov. 25, 1921, in the village of Hameringham, Lincolnshire, in the East Midlands of England. His father was a foreman on a local farm, and his mother died when Leonard, as he was mostly known then, was very young.

They were a poor family who lived in a farmhouse with no electricity or inside toilet. His only friends, he wrote later, were his sister Lena — “my surrogate mother” — and his pet pig.

At age 11, he went to a boarding school in Hampshire, run by a charity that looked after orphans or farm children who had lost a parent. After enjoying mostly athletics at school, he left at 18 in 1939 and worked as a park keeper before — with war having broken out — he volunteered for the RAF. He trained for a time in Florida and gained the nickname “Johnny.”

Before the Ruhr raids, Mr. Johnson took part in many Lancaster bombing attacks with McCarthy as his pilot. In December 1942, while bombing Munich, they were badly hit and almost shot down by Luftwaffe fighter planes but made it back to England with one engine gone. Mr. Johnson always said McCarthy was the best Lancaster pilot he had ever flown with.

After the war, he served the RAF in various training roles, retiring in 1962 with the rank of squadron leader. He later became a teacher, including at mental health institutions, and was active in his local Conservative Party.

He married Gwyneth Morgan in 1943. She died in 2005. Survivors include three children, eight grandchildren and 18 great-grandchildren, according to the Guardian. Queen Elizabeth II named him a Member of the Order of the British Empire in 2017.

Asked whether he was scared during the Dambuster raid, Mr. Johnson said, according to the Times of London: “What was going on didn’t bother me in the least. My job was to get that bomb as near as possible to that mark. I was concentrating on that.”