Wörthersee Swim Austria

Glacial depths characterize Lake Wörthersee, where swimmers stroke across sixteen kilometers of open water. The Wörthersee Swim Austria is an open water swimming event staged in Lake Wörthersee in Klagenfurt, within the southern Austrian state of Carinthia. It has earned a reputation as the biggest swimming adventure in the Alps. Organized by the Wörthersee Swimming Club, this multi-race gathering gained international recognition when it was nominated for the 2021 World Open Water Swimming Event of the Year Award. The competition offers an extensive program of distances catering to every level of endurance, starting with sprints of 500, 600, 1,000, and 1,500 meters up to 3,000 and 5,000 meters. For marathon swimmers seeking prolonged time in the water, the event features grueling distances of 10,000, 17,000, and an extraordinary 34,000 meters.

Swimmers assemble on the lake's southern shore at Strandbad Maiernigg before setting out across the open expanse. In past editions, participants have boarded boat shuttles that carry them up the lake to offshore start lines, swimming back toward the Klagenfurt shoreline within dedicated corridors shielded from regular boat traffic. In special nighttime race formats, the lake has transformed into a glowing sea of lights, with swimmers following luminous buoys and safety glow sticks under the dark sky.

Lake Wörthersee: Alpine warmth, glacial depths, and the Glanfurt outlet

Carved into the Southern Austrian landscape during the last ice age by slow-moving glaciers, Lake Wörthersee extends for 16.5 kilometers while spanning roughly 1.5 kilometers across its widest reaches. It forms an elongated hydrographic basin divided naturally into three distinct segments. The entire lake system discharges through a single surface outlet, the Glanfurt river, which carries its outflow away. While cold winter cycles bring freezing conditions that lock the lake under ice about once every ten years, summer paints an entirely different picture. Lake Wörthersee is celebrated as the warmest of the large Alpine lakes. Driven by summer sunshine, surface water temperatures regularly reach 25 degrees Celsius, allowing swimmers to log immense mileage without battling the numbing cold common to high-altitude venues.

What elevates every stroke is the remarkable clarity of the water, which maintains near-drinking water purity across the entire course. Looking down through the surface, you see clean depths. Glacial dynamics have sculpted nearby bodies of water across the broader Carinthian lake district. Fed primarily by Tiebel Creek in its eastern bay, Ossiach is a dimictic lake that mixes its water layers in spring and late autumn, while its summer surface warms up to 28 degrees Celsius along shores lined by quiet natural reserves. In the neighboring tectonic valleys, smaller glacial waters like Keutschacher See and Hafnersee tell a similar story. Keutschacher See reaches a depth of 15.6 meters, with sandy moorland covered in sedge and reeds lining its protected western shores.

Beneath its surface lie submerged oak trunks from a prehistoric stilt village, dated by dendrochronology to 3947 and 3871 BC when the water level was 1.5 meters lower. Nearby Hafnersee, formed by a side arm of the Drau glacier, features twin basins separated by a shallow bar only 1.8 meters deep, where humic acids from surrounding moors lend the water a natural brown hue, reaching 25 degrees Celsius in late July above submerged Neolithic pile dwellings discovered in 1974.

Pörtschach, Kapuzinerinsel, and Blumeninsel: the lake's underwater thresholds

The lake owes its identity to its islands, having been called Werdersee, or Island Lake, until the 19th century. A submerged rock threshold crosses the bed of the lake between the Pörtschach peninsula and Maria Wörth, marking the boundary of the smallest of the three basins. Along the northern bank, the Pörtschach peninsula juts into the open water, connected to the mainland on its northern side. Farther to the west, long stretches of seawall border the shoreline, providing a crisp architectural perimeter against the blue water. In the open lake, only two true islands break the surface: Kapuzinerinsel and Blumeninsel. The uninhabited Kapuzinerinsel rises as a small, wooded sanctuary frequently visited by swimmers and local day-trippers in rental boats.

Blumeninsel is a 470-meter-long and 95-meter-wide island that emerged above the surface in 1770 when artificial modifications lowered the lake level. That historical reduction in water made the passage between the island and the peninsula too shallow for commercial shipping to navigate, leaving behind a tranquil channel. Locally remembered under the old moniker Snake Island, the name refers strictly to the long, winding outline of the landmass rather than any presence of reptiles. Today, a protected landscape area safeguards this scenic islet, preserving its peaceful setting within the open lake.

Strandbad Maiernigg and the Maria Loretto shoreline

Race operations center on Strandbad Maiernigg, a green lakeside facility located on the southern bank of Lake Wörthersee. Situated within Klagenfurt am Wörthersee, the largest city in Carinthia and the sixth largest in Austria, the lido welcomes swimmers from the immediate region and far beyond. At Strandbad Maiernigg, a shaded forest path leads up into the trees to the historic composing hut of Gustav Mahler. The short trail offers swimmers a serene post-race stroll through the woods. The Maria Loretto peninsula extends into the water, crowned by a stately historic mansion acquired by the city. A historic canal still branches off toward the urban center, originally built to transport timber and supply water to the town's defensive moats. Standing on the green lawns at Maiernigg after completing your swim, you find yourself at the crossroads of cultural history, mountain air, and the gentle, pristine waters of Lake Wörthersee.