Devon Pendleton wrote an article about the World's Most Grueling Sporting Events in Forbes Magazine.
Devon included the Manhattan Island Marathon Swim. His list included the following:
1. Atlantic Rowing Race, a 4,633K (2,879-mile) rowing race across the Atlantic Ocean from the Canary Islands to the Caribbean. Note: if you thought open water swimming entry fees are expensive, entry fees for the race are US$24,000 for a solo rower and US$48,000 for a four-person team, not including enough food and supplies to last 120 days at sea.
2. Badwater Ultramarathon, the world's toughest foot race, 217K (135 miles) from California's Death Valley, the lowest point in North America, to Mt. Whitney, the highest peak in the continental USA.
3. Ironman Triathlon, a 3.8K (2.4-mile) swim (originally based on the Waikiki Roughwater Swim), 290K (180-mile) bike ride and a 42K (26.2-mile) run.
4. Grappling where combatants fight their opponents with leg locks, arm locks or choke holds.
5. Manhattan Island Marathon Swim, a 45.8K (28.5-mile) swim around New York City (see above).
6. Pro boxing.
7. Tour De France, the 21-day, 23-stage cycling race of sprints and mountain climbs.
8. Ultimate Fighting Championship, a brutal mix of full-contact mixed martial arts fighting.
9. Yukon River 1,000, the longest canoe and kayak race in the world: 1,609K (1,000 miles) of paddling along the Yukon River.
AP photo of Manhattan Island Marathon Swim by Emile Wamsteker.