Open Swim Harmonie Mutuelle Gérardmer

On the final Saturday of June, the streets of Gérardmer transform as swarms of swimmers emerge from the timber-framed hotels, heading toward the shoreline while the morning mist still clings to the surrounding Vosges peaks. Local residents, accustomed to the rhythmic pulse of this mountain town, gather along the promenade to witness the start of the Open Swim Stars, an event that brings a distinct competitive edge to the basin held in place by the massive terminal moraine of the Würm glaciation. Swimmers lining up for the 4,500-meter course look out over a landscape shaped by ice retreats that ended 10,000 years ago, knowing that beneath the surface lies a maximum depth of 38.40 meters, specifically in the channel between Kattendycke and Croix Meyon.

Historical currents and the water

Navigating these depths requires an awareness of the lake’s hydrology, particularly near the northeast sector where historical cleanup efforts removed 120 tons of munitions, yet residual traces of lead and TNT persist in the silt. Athletes follow a path that skirts the legacy of the 'Sea of Saint Gerard', a name tracing back to the 14th-century veneration of the Bishop of Toul. While modern currents remain stable, one must consider the influence of the Jamagne river, which acts as the lake’s primary emissary by draining water toward the Vologne. This specific aquatic environment was navigated in 1908 by Marie Marvingt, a pioneer whose long-distance endurance feats included significantly longer crossings in the Mediterranean, marking the lake as a historic site for French open water swimming.

Participants can select distances ranging from 500 to 4,500 meters, with the event logistics managed by the OpenSwim organization to ensure safety across the varying depths. Water temperatures in late June typically stabilize, but the altitude of the Vosges ensures the surface remains brisk for those unaccustomed to mountain lakes. By the time the final group exits the water, the connection between the modern athlete and the 1908 legacy is confirmed by the same stillness of the water near the Jamagne outlet.