Escaping the escape-proof Rock is one of the many challenges of San Francisco's Alcatraz triathlon

The Escape From Alcatraz Triathlon, now in its 34th year, has been one of the world's best and most popular triathlons, in large part because of the allure of the 1.5-mile bone-chilling swim from Alcatraz through the swift currents of San Francisco Bay. My story for ESPN.com's Endurance Sports section: http://espn.go.com/sports/endurance/story/_/id/11002656/endurance-sports-escape-alcatraz-triathlon-offers-unique-challenges