Anthony Smith, second from right, led a transatlantic crossing by raft in 2011, when he was 85. From left, crew members are John Russell, David Hildred, Mr. Smith and Andrew Bainbridge. (Judy Fitzpatrick/AP)

Anthony Smith, a British author, explorer and inveterate adventurer who in his mid-80s — against the advice of well-meaning doubters — voyaged across the Atlantic Ocean on a sail-powered raft, died July 7 at a hospital in Oxford, England. He was 88.

The cause was acute respiratory failure, a Web site titled An-Tiki that is devoted to Smith and his exploits quoted Mr. Smith’s son as saying.

Trained in science at Oxford University, Mr. Smith was a sailor, airplane pilot and balloonist. He traveled the length of Africa in both directions by motorcycle. He was seen frequently on television, was a correspondent for British newspapers and more than two dozen books carry his name as author.

But the voyage he planned in his 80s led people to question his sanity.

“Other people use that word, mad, all the time,” he said in an interview for Tourism Today after his crossing. “But I was determined,” he said. “So I just went ahead and did it.”

Mr. Smith’s five children, he told an interviewer, were not “totally cooperative.”

His raft was named Antiki, a reference to Thor Heyerdahl’s Kon-Tiki, which made a celebrated Pacific Ocean voyage in 1947.

Crew members for Mr. Smith’s expedition were recruited through an advertisement seeking older people who were “serious adventurers only.” Mr. Smith and his crew of three — Andrew Bainbridge, David Hildred and John Russell, none younger than 56 — set sail from the Canary Islands on Jan. 30, 2011.

No great sailing skill was demanded of those aboard the Antiki, which measured about 20-by-40 feet, and rested on an array of plastic pipes. The raft had no motor and was powered by a single sail.

“You don’t have to do much,” Mr. Smith said of navigating his craft. “The wind and the current take you.”

Not without hardships and hazards, however.

In the first week, the raft’s two rudders broke. After about three weeks, the supply of fresh food was gone. In 10 weeks, wind, current and the whim of the waves took Mr. Smith from the Canary Islands, off the African Coast, to the Caribbean island of St. Martin, which he reached on April 6 after more than two months at sea.

Raft travel was slow going. Sailing day and night, Mr. Smith and his crew made their way across the ocean vastness at about 2.4 miles an hour.

Because Mr. Smith missed his original destination of Eleuthera in the Bahamas, he embarked on a second trip in 2012, sailing from St. Martin to Eleuthera with a crew of two women and three men.

His voyage was inspired by his interest in a World War II story of survival at sea. After their ship was sunk, two British sailors drifted across the Atlantic in an 18-foot boat for 70 days before landing at Eleuthera.

“That whole story fascinated me,” Mr Smith said. As a young man, lack of funds kept him from trying to duplicate the voyage, and later it was job responsibilities. Finally, he said, when he became “very much older,” the idea of a raft voyage still gripped him.

Mourning for a lost youth was not for him. “Am I supposed to potter about, pruning roses and admiring pretty girls,” he asked. “Or should I do something to justify my existence?”

Anthony Smith was born March 30, 1926, in the English county of Buckinghamshire and grew up on the celebrated estate of the Astor family, Cliveden, which was managed by his father.

During World War II, Mr. Smith served in the Royal Air Force Reserves. At Oxford, he studied zoology and as a young man made an expedition to Iran, exploring underwater tunnels and discovering a new living species of fish, which was named for him.

Later he wrote for the Manchester Guardian, as the British newspaper was then known. He left to head a South African magazine called Drum, which he described as “the voice of black unrest.”

His return trip to England was made by motorcycle. He again worked for the Guardian and later spent six years as science correspondent for the Daily Telegraph.

On leave from that job, he flew a hydrogen-filled balloon around Africa — a trip that supplied material for another book. He was believed to be the first Briton to make a balloon crossing of the Alps.

As a founder and longtime head of the British Balloon and Airship Club, he was a consultant on the airship sciences in the films “Chitty Chitty Bang Bang” (1968) and “Superman II” (1980).

Mr. Smith was also the author of “The Body” (1968), which was praised by commentator Alistair Cooke as a masterpiece and became a best-seller. Years later, Mr. Smith published a companion volume, “The Mind.”

He continued to make other expeditions by boat and balloon, which led to more books. Mr. Smith also appeared on radio and television shows about nature and geography.

His raft voyage generated still another book, “The Old Man and The Sea,” which is scheduled to be published in February.

His marriages to Barbara Newman and Margaret Ann Holloway ended in divorce. According to a report in the Telegraph, survivors include three children from his first marriage; a son from his second; and a daughter from another relationship.

As justification for confronting the hazards of the sea at an advanced age, Mr. Smith would quote a line from T.S. Eliot’s “Four Quartets,” saying, “ ‘Old men ought to be explorers.’ ”