The Half Distance Triathlon Des Moines Swim Course (1.9 KM) Kick off your race at the iconic Gray's Lake Peninsula. The spectator-friendly swim course allows your support crew to cheer you on from Gray's Lake Bridge, giving them a perfect view of your entire swim. You'll finish just steps from the Transition area in Gray's Lake Park. Average water temperature: 72°F (22°C). Bike Course (56 Miles) Embark on a scenic ride from downtown Des Moines to the picturesque countryside of West Des ...