Most of the classes start on the stationary bikes, but there is swimming involved too.
Students of the class say the stationary bike teaches them technique that will help them on the 'real' bike.
The class meets three times a week, and you train as a group.
Eight weeks ago, Joe Hornstein couldn't do one lap, but now he's a triathathalon competitor.
"I think what you get is an accomplishment which most people will never experience, and when you can share that story with your friends and family it's a pretty big deal," says Joe Hornstein.
For more information on the classes, go to www.chelseapiers.com/sc/triathlon.htm .