The Horsetooth Open Water Swim is the only time swimmers are able to swim from end-to-end of Horsetooth Reservoir. It's one of the few high altitude, long distance, cold water swims available to swimmers and is ranked the 38th best open water swim in the US. The distances are 10 km, 2.4 mile, 1.2 mile, 1000 m and 250 m swims. It is also a fundraiser for Partners Mentoring Youth, Fort Collins. Pre-registration is required. Spectators are welcome.