Jason Zirganos of Volos, Greece, was one of 25 international swimmers who entered for the English Channel swim from France to England in 1950. (Leslie Priest/AP)

People die swimming the English Channel because they refuse to give up until it’s too late.

The exact number who have died attempting the swim isn’t known. The Channel Swimming & Piloting Federation lists eight deaths between 1926 and 2013. Its older rival, the Channel Swimming Association, lists seven, including three who weren’t swimming under the organization’s supervision or seeking its certification.

Whatever it may be, the number is astonishingly small given that 1,400 people have swum the 21 miles between England and France, and thousands more have tried and failed.

The circumstances leading to death are hard to determine. But it’s a good guess that the final minutes involve a struggle between determination and physiology, with determination winning.

In July 2012, a 45-year-old man from Ireland died about a half-mile from the coast of France. Last July, a 34-year-old Englishwoman died a mile from the same shore. Both had been in 60-degree water for 16 hours without wet suits.

Jason Zirganos swam the English Channel four times. But in a 1958 swim from Ireland to Scotland, he lost consciousness and was pulled from the water. (Tom Fitzsimmons/AP)

The currents off Cap Gris-Nez, the intended landfall, are notoriously unpredictable, sometimes carrying swimmers sideways and stalling forward progress for hours. (In the past, some people swam from France to England, but the French government now prohibits departures from its shores, so everyone leaves from England.)

One hazard of Channel swimming is not shared by other sports: Its best practitioners may be able to literally compete unconsciously.

Unconsciousness occurs when the core body temperature reaches 91 to 86 degrees. Muscles, however, can function down to about 81 degrees. That means a person who is highly acclimated to the cold, with great willpower and the mechanics of swimming burned into muscle memory, can swim for a short period beyond the point at which his brain is too cold to be fully conscious.

That appears to have been the case with Jason Zirganos.

A major in the Greek army, Zirganos was one of the great open-water swimmers of the mid-20th century. His tolerance for cold water and his ability to maintain his core temperature in it was studied by British scientists, who reported their findings in the Lancet in 1955.

Zirganos swam the Channel four times between 1949 and 1954. In 1953, he swam in the Bosporus in 46-degree water for four hours before being pulled out semi-conscious. He did not regain full consciousness for three hours. His trainer thought he’d been poisoned.

In 1958, Zirganos tried to swim from Ireland to Scotland across the 22-mile North Channel of the Irish Sea. The water temperature ranged from 49 to 53 degrees. After six hours and just three miles from Scotland, he lost consciousness and was pulled into the boat following him. A physician cut open his chest and squeezed his fibrillating heart.

“Open cardiac massage in a rowboat is unlikely to be successful,” said Michael J. Tipton, an exercise physiologist at the University of Portsmouth, in England, who described the event in a scientific paper last year.

Indeed: Zirganos died in the boat at age 46.