Swimming takes place in the 50-metre outdoor pool of Buchs. 3.8 kilometers corresponds to 76 laps. In recent years the water temperature in August has been between 21 and 24 degrees Celsius. The pool is equipped with solar heating, which runs at full speed during the swissultra races. 

Up to eight athletes swim in each lane. A maximum of five lanes are available. The number of swimmers per lane depends on the number of participants.


During the swim the athletes may be supported from the opposite side of the pool. Liquid food may be deposited at the edge of the pool. The athlete must leave the pool to eat. The lanes are counted by volunteers who also show the last 100 meters. The swimming caps are provided by swissultra and are mandatory. A wetsuit is obligatory; neoprene booties or gloves are not allowed. 


Basically swimming takes place in all sorts of weather, even in light rain. Exceptions are thunderstorms and storms with lightning. The race marshals decides if, when and for how long the swimming is interrupted and inform about the further procedure (break with restart, interruption or replacement).