His first, Push the Limit, scheduled to be released in June, uses the Kinect hands-free control sensor for Microsoft's Xbox 360 system in lieu of a pool. Players stand upright and work their arms — no kicking required — in a variety of swimming stroke motions as they advance from introductory swim meets to championships.
"The better stroke technique you have, the faster you go," Phelps says.
"It's extremely realistic. If you had asked me five years ago if I ever thought I would have a video game coming out with swimming in it, I'm not sure what I would have said. I would never ever have thought it would be like it is. It is cool and fun."