Many triathletes point to the swim as a triathlon’s most stressful segment. Most swims take place in open, often cold, water with hundreds or even thousands of other swimmers vying for position. “Nothing can prepare a newbie for the start,” said Russ Evenhuis, a triathlete in Olympia, Wash. “It can be like jumping into a washing machine. You will get swum over, kicked, hit and banged into.” A triathlon’s open-water swim hardly resembles the pools where most triathletes train, said Neil Cook, a New York City based triathlete and coach. “There is no wall 25 yards away, you can’t see the bottom and the 50 to 150 people around you are more than you’ve probably swam with in total during your training,” he said. “Oh, and you are wearing this wetsuit that’s tighter than a girdle and you can’t breathe.” Raise your heart rate and blood pressure under these conditions, he said, and “any weakness you have will become apparent.