The Jim McDonnell Lake Swims are a 2-day event in Reston VA, May 27-28 2017. Saturday May 27th offers a 1 mile Practice Swim on the race course. Sunday May 28th has 2 races, 1 mile race and 2 mile race. Water temperatures are usually in the 70's F, and both CAT I and CAT II swimwear can be accommodated. The Jim McDonnell Lake Swims are now in its 30th year.