The superb Fontanil beach is easily accessible by the N81 bus (air-conditioned and connected to the public transport network) from Vénissieux train station. The water quality is excellent for swimming, and there is lifeguard supervision (flags, lifeguards).
A lake not far from Lyon (city center) accessible to everyone.
There are several beaches to enjoy during the day and escape the city; you can even find a naturist beach.
I'm discovering this area a bit more because I've been here several times, but not always to the same spots.
The water looks clean.
We spend a lovely afternoon on a hot day on Monday. We did get there by bus, the N80 going there didn't seem to leave as per schedule so a bit long to get there from Lyon/Villeurbanne but worth the time. Clean and calm water at pleasant temperature. Nice lake to swim in. The Brasserie of the Morlet plage was not crowded and we did spend some time there playing cards while eating our ice creams.
Lake with equipped beaches. Several different atmospheres available depending on the area visited. Children's play area, shaded walks, and all kinds of food available.