If running 25km sounds difficult, try swimming the distance through a churning, wind-swept sea amid a thrashing mob while the scorching sun bakes your back.
That's the life of open-water swimmers, the curiously content marathoners at this week's swimming World Championships.
"It's definitely more fun going out into the ocean or a lake as opposed to doing laps and flip turns in a pool all day," said 17-year-old American Chip Peterson, a silver medalist in Sunday's 5km race, the first of three open-water events in the weeklong competition.
Peterson finished second to Germany's Thomas Lurz, who won the 5km in 51 minutes, 17 seconds. On the women's side, 16-year-old Russian Larisa Ilchenko took the women's gold in 55 minutes, 40 seconds.
The 10km race is today and the men's and women's 25km events are this weekend.
Though the roots of the sport can be traced to the first crossings of the English Channel in the late 1800s, it's relatively new in its current form. FINA, swimming's world governing body, didn't recognizing open-water racing until 1986 and it stzill isn't in the Olympics.
US coach Rick Walker thinks it will get there soon.
"There's no reason it shouldn't. I see this as the purest form of swimming, in an uncontrolled environment, where there are no walls or barriers," he said.
In Montreal, the competitors are finding conditions more placid than they encounter in other parts of the world, where races are held in jungle rivers, mountain lakes or expanses of ocean.
Here, competitors are racing in a glassy enclosed basin that was used as the rowing venue in the 1976 Olympics. The freshwater is pumped in from the nearby St. Lawrence River.
The calm surface belies how violent things can get under the water, mostly in the shorter races. The two dozen or more swimmers shove, grab, kick and tug other competitors' bathing suits for an edge. On Sunday, four-time world champion Edith Van Dijk took a shot in the mouth while winning the bronze in the 5km.
Referees oversee the races from small pontoons and can disqualify swimmers for interference.
FINA also has set conditions for open-water venues -- minor currents, a minimum water temperature of 14?C and a minimum depth of 1m.
But the parameters still provide wide variation. One recent race was contested in the Parana River in Argentina. Another crossed Lake Geneva in the Swiss Alps. A Hong Kong event plunged swimmers into the Indian Ocean.