SWIMBIKE des 3 Lacs begins at Lac de Naussac in Lozère, sending small teams out for three days of road cycling and open-water swimming. The format is itinerant, moving through the lake country of Ardèche, Haute-Loire, and Lozère, with stages centered around Lac du Bouchet, Lac d’Issarlès, and Lac de Naussac.
Each team has three or four participants. The event is run without an overall ranking or a clock. Riders cycle from Naussac to a mountain lake, swim there, then return by bike on a different route; the next day repeats the concept at another lake. Across the full event, participants swim 9 km and ride about 220 km, making it more of a shared endurance trip than a standard race.