Four swims in this series equal one 13.1-mile half marathon. The first swim is a 1- or 2-mile cruise through Lake Harriet in June. The most intimidating swim comes next, a 5-mile point-to-point in Lake Minnetonka in July. (You’ll need a friend to accompany you via kayak or canoe, per event rules.) Then there’s the Lake Rebecca 5K in August followed by another 1- or 2-mile plunge in Lake Minnetonka in September. Do the max on all four and it’s a half marathon. Less experienced swimmers could go for the Perch Lake swim near Hudson, Wis., in August. The lake is spring fed and placid. The course is a 1- or 2-mile loop. Swimmer’s choice.