Ironman Switzerland Thun, where the convergence of endurance and stunning landscapes creates an unforgettable triathlon experience in the heart of Thun, Switzerland. Swim: Begin your journey with a one-loop 3.8 km (2.4 mile) swim that immerses you in the crystal-clear waters of Lake Thun. The renovated lido serves as your starting point, providing athletes with a gateway to an aquatic adventure amid the Alpine beauty. With an average water temperature of 66°F (19°C), the swim sets the stage ...