Chiemsee Vollmondschwimmen

Under the midsummer full moon, the quiet surface of Lake Chiemsee glows in the dark as an illuminated fleet of swimmers strikes out into open water. The Chiemsee Vollmondschwimmen is an open water swimming race held in the freshwater of Lake Chiemsee at Prien am Chiemsee, in the state of Bavaria. Held at night under the light of the full moon in July, the event is one of the most distinctive nocturnal challenges on the German open water circuit. The competition centers on a single 2-kilometer race that follows a triangular course starting from the lido at Schraml-Strandbad. Swimmers plunge into the lake after dark, navigating directly towards the dark mass of the Herreninsel, completing a leg that runs parallel to the island's shores before heading back across open water to the departure beach.

Sighting across the lake in total darkness demands sharp concentration, particularly when harbor lights along the mainland create optical confusion across the surface. To guarantee complete safety, every swimmer is required to wear an illuminated LED light, keeping the entire field visible to the water rescue teams patrolling the course in accompanying boats. Organized under the umbrella of the Alpen Open Water Cup, the Vollmondschwimmen brings together passionate long-distance amateurs and world-class competitors. Elite athletes such as Florian Wellbrock and Rob Muffels have dived into the night crossing at Prien, demonstrating the sporting stature of this alpine night swim.

Lake Chiemsee from Würm glaciation to the Prien river

Lake Chiemsee was formed approximately 10,000 years ago as a vast glacial basin left behind at the end of the Würm glaciation. The lake extends over an 83-kilometer shoreline including its islands. Beneath the surface, the lake bottom drops into submerged hollows, reaching its deepest point at the Unschuldige-Kinder-Grube at a depth of 73.4 meters. The lake receives fresh inflow from several tributaries, most notably the Prien, which flows for 33 kilometers before emptying into Lake Chiemsee at the bay of Schafwaschener Bucht. Originating at an elevation of 1,150 meters near the Spitzstein peak, the Prien ranks as one of the longest mountain streams in the Bavarian Alps and represents the second-largest tributary entering the lake.

A weir on the Prien also feeds the Mühlbach, an independent watercourse that carves its own route into the lake basin. Between 1902 and 1904, major engineering work lowered the water level of the Chiemsee by 70 centimeters, draining substantial parcels of wetlands along the rim of the basin. Just 540 meters from the southern shore of Lake Chiemsee sits the Förchensee, a natural lake whose surface outflow currently drains northeast along the Unterer Förchengraben, even though historical surveys indicate it once drained northwest straight into the Chiemsee. To the northwest of the main lake lies the Stettner See, part of the protected Eggstätt-Hemhofer lake plateau, which functions as an entirely closed kettle lake with no surface inlets or outlets whatsoever.

Herreninsel and Fraueninsel: royal retreats and medieval abbeys

The turnaround point of the race course is anchored off the Herreninsel, the largest of the three Chiemsee islands, covering an area of 238 hectares. In 1873, King Ludwig II intervened to purchase Herreninsel for 350,000 guilders, thwarting a commercial logging venture that would have clear-cut its ancient woodlands. Today, an eight-kilometer walking path circles near the island shore, rising at its southwestern corner to a scenic viewpoint elevated 20 meters above the lake level. On Lake Chiemsee's northwest shore, the 38-hectare Urfahrn peninsula stretches approximately one kilometer into the water to the Scheren headland, lying just 300 meters from the northern tip of the Herreninsel. Fraueninsel is the second largest island in Lake Chiemsee, circled by a pleasant 1.5-kilometer footpath. Here, Duke Tassilo III of Bavaria established the Benedictine nunnery of Frauenwörth in the eighth century, a religious community that still lives on the island.

Schraml-Strandbad and the protected shores of Prien

The start and finish line at Schraml-Strandbad provides an inviting venue for swimmers and spectators alike. The beach features an extensive lawn for sunbathing that offers expansive panoramic views across the water toward the Herreninsel and the Alps. The lake bed shelves gently away from the grass, offering an exceptionally flat water entry that ensures an effortless wade out into swimming depth. Water quality across the bathing area has been consistently rated as excellent, providing clean and pristine freshwater for competitive swimming. During normal hours, the lido operates rentals for rowing boats, pedal craft, sailing boats, and electric cruisers, with a designated zone at the far end of the property that permits dog bathing.

A rustic alpine wooden hut on the grounds serves as a focal point for social gatherings and lakeside events. Just down the shoreline, Prien serves as the principal home port for the Chiemsee passenger fleet, where the vintage paddle steamer Ludwig Fessler, built in 1926, remains in active service. The natural environment surrounding Prien and the Chiemsee is shielded by comprehensive conservation measures. The lake and its islands are governed by a dedicated landscape conservation ordinance, protected as an EU bird sanctuary and designated habitat for native flora and fauna.

Lake Chiemsee is recognized internationally under the Ramsar Convention as an aquatic ecosystem of global importance. On the lake's northwest shore, the 67-hectare Sassau peninsula extends 1,800 meters into the water to the Kailbacher Eck, bordered by a dense reed belt between 110 and 230 meters wide and rising to 17 meters above the lake.