Vättern is the second-largest lake in Sweden, deep, cold, and unusually clear — visibility of ten metres or more is normal. From Hjo the easiest entry points are the small beach in the spa park and the jetty in the harbour. Both have changing huts and shallow access.
The lake warms slowly: water temperatures in May and June are bracing even by Swedish standards, and most locals do not swim seriously until July. By August it is usually pleasant. Vättern is also a popular spot for open-water swimming events.