Starnberger See Längsdurchquerung Seeshaupt–Percha

In February 1929, the frozen surface of Lake Starnberg became a makeshift laboratory for speed when rocket pioneer Max Valier launched his sled, the Rak BOB II, across the ice at a staggering 400 km/h near the historic Undosa bathhouse. This daring spectacle stands in stark contrast to the rhythmic, measured pace of modern endurance swimmers who now traverse these same waters during the annual Starnberger See Längsdurchquerung. While the 1905-built Undosa facility once redefined leisure as one of Germany’s earliest wave pools, today’s participants focus on the 19.7-kilometer point-to-point course that stretches from Possenhofen to Leoni.

The water and the path

Navigating this glacial basin, created during the Würm glaciation, requires more than just stamina; it demands respect for the lake's dramatic topography. As you swim, you pass over the Allmannshauser Steilwand, a sheer underwater wall that plunges to 70 meters, marking the deepest and steepest descent in German inland waters. Beneath your stroke, history remains submerged near the Roseninsel, where excavations have uncovered bronze fish-hooks and ancient dugout canoes dating back three millennia. The surrounding landscape, framed by terminal moraines and the distant silhouette of the Ilkahöhe, offers a constant point of orientation as you complete your transit. Those seeking a shorter challenge later in the season might look toward the Seeüberquerung from Tutzing to Ammerland.

Race day logistics

Organized by Active Concepts, the event has grown into a significant fixture, often reaching full capacity well before the August start date. Wetsuits are permitted, providing additional buoyancy and warmth for the long-distance effort. The logistics of such a major crossing are supported by the DLRG and local water rescue services, ensuring safety across the expansive distance. Every finisher receives a commemorative T-shirt, a small token for completing a journey through a site once graced by the opulent courtly festivals of the 17th-century Bucentaur royal barge. While the lake remains a sanctuary for tens of thousands of migratory birds, the focus on race day remains entirely on the clear, deep waters that have hosted organized swimming competitions since the German Championships of 1908.