Amateurs are making a splash* in lakes, rivers and oceans

This summer Diana Nyad, at the age of 62, will try something she has tried and failed to do three times: to swim the 103 miles from Cuba to Florida, braving venomous jellyfish, sharks, skin by salt water, the inevitable of the tongue and hallucinations.

The American marathon swimmer first attempted the in 1978 when she was 28, swimming 50 miles, or 80 kilometers, in 41 hours and 49 minutes before currents pushed her so far off course that she had to abandon her mission. Not long after, she swimming until she 60 and felt the what no human had yet done without the protection of a shark cage.

After months of preparation, she from near Havana in August, but an asthma attack forced her to abort after 51 miles and 28 hours. In another attempt in September, jellyfish stings made her so sick that she had after 92 miles and 40 hours. Afterward, she swore never to try it again but has since

Whether she fails or succeeds, Nyad has brought worldwide attention to the growing sport of open-water swimming. Amateur athletes around the globe are the pool and instead into lakes, rivers and oceans. Long-distance open water swimming has since 1875, when the British captain Matthew Webb became the first to swim across the English Channel.

A major of open-water swimming in recent years has been an explosion in the popularity of triathlons, which combine cycling and running with a long swim that often takes place in open water rather than in the confines of a concrete pool. In the United States alone, an estimated 2.3 million individuals completed triathlons in 2010, up 55 percent from the year earlier, according to a report in August by the Sporting Goods Manufacturers Association. Growth rates are similar in many other rich countries.

The triathlon finally became a medal sport in the Sydney Olympic games of 2000, bringing a niche activity into the . Television coverage of big events like the Hawaii Ironman, and the proliferation of smaller offroad events like the Xterra series of races have many new participants. In 2008 at the Beijing Olympics, a 10-kilometer open-water swim was a medal event for the first time.

Swimming has often been the greatest for many aspiring triathletes because it is often more difficult than cycling and running. As a result, specialized open-water swimming courses are

Terry Laughlin, an American swimming coach, has developed a technique called Total Immersion that teaches people to use balance and energy conservation to help them . He has built an international network of coaches who conduct periodic workshops the world over. Next up are clinics in Hawaii in March and Puerto Rico in April. (I participated in a similar clinic in the Swiss Alps several years ago.)

A British company called SwimTrek conducts swimming holidays and tours in the Mediterranean, Caribbean, Middle East and elsewhere. For example, it hosts a seven-day course on the islands off the Dalmatian coast of Croatia. Participants swim on average four kilometers a day, and the price starts at about 750 pounds, or $1,200.

Many are learning later in life, something Nyad has always encouraged. About 20 years ago, while living in New York City, Nyad would go upstate with a close friend, Candace Hogan, who grew up as a land beast: "Quick on the track, great on the softball field, agile in a soccer game. But she never had exposure to pools or the ocean and never learned how to swim," Nyad wrote recently on her blog in a post called "It's never too late." Now Hogan can swim miles off the coast into the ocean.

Hiromu Inada of Japan started doing triathlons at the age of 69. He completed his first Ironman, in South Korea, in 2011 at the age of 79. (A full Ironman event is an extraordinary feat that includes a 2.4-mile swim, a 112-mile bike ride and a 26.2-mile run.) A few months ago, he competed a half Ironman in Laguna Phuket .

Just as many marathon runners try to run on each of the seven continents, and many mountaineers for seven of the world's major peaks, swimmers have their own . Forty-eight individuals hold the Triple Crown of Open Water Swimming, which requires having completed three marathon swims: 33.7 kilometers across the English Channel; 33.7 km across the Catalina Channel in southern California; and 45.8 km around Manhattan.

No one is known to have completed the Ocean's Seven, which in addition to the English and Catalina Channels, includes the Cook Straight between the north and south islands of New Zealand and the Tsugaru Channel between Honshu and Hokkaido islands in Japan.

Of course, most swimmers don't have such grand aspirations. On Saturday and Sunday in South Africa, the Midmar Mile takes place. It is the world's largest open-water swim race. And it is just a mile. It was swum for the first time in 1973 with 153 competitors. The event now draws about 16,000 entries.

Zports, a company established in 2007 by Mike Zoetmulder that promotes sports in South Africa, has organized a 16-day tour called the African Swimming Safari. Participants begin with the Midmar swim and end with the Redhouse River Mile, the continent's oldest open-water event, now in its 88th year.

Though open-water swimming sounds risks, swimming in general has its health benefits.

The main danger seems to occur during the stress of racing conditions. Last August, two people died after suffering heart attacks during the swim of the New York City Triathlon. According to a study conducted by the American College of Cardiology, the risk of sudden death in a triathlon is about twice that of a marathon. A study in The Journal of the American Medical Association showed that of 14 deaths that occurred in triathlons between 2006 and 2008, 13 took place during the swimming portion. The study found that most of those who had died already had heart conditions.

As Nyad prepares for another attempt at her Cuba-to-Florida journey this summer, she seems to have a realistic mindset for what might be her final at something no person has yet done.

"The sport is sort of a microcosm of life itself," she said in a speech posted last month on her Web site. "First of all you're gonna hit obstacles. And even though you are feeling great at any one moment, don't . Be ready because there is going to be pain. There is going to be suffering. It's not going to feel this good all the way across." *