Lac De Saint Cassien
This is a natural lake where no boats with fuel driven engines are allowed. Very warm waters. You can camp or sit at the lakeside, or you can use a beach club. Perfect for spending a day – also, there are plenty of activities to book https://www.experiencecotedazur.com/en/destination-cote-dazur/pays-de-fayence/saint-cassien-lake/.