The Lac de Joux lies in a high valley of the same name. It is remarkable in that no surface flows out of it. There is a motorboat service in summer from Le Pont to the other end of the lake.
Lac de Joux and the nearly adjacent but much smaller Lac Brenet have no surface drainage: the water trickles away underground and only comes to the surface again a few kilometres away near Vallorbe. In July and August there is just one scheduled boat service every day on the Lac de Joux, doing a round trip in the afternoons, starting at Le Pont at the north-eastern end of the lake. In June and September, the boat only runs on Saturdays and Sundays. This makes the Lac de Joux shipping company one of the smallest in Switzerland, and a ride on the lake something really special.