Lake Merced, San Francisco. Accessible from Parkside Aquatic Park. You can carry a canoe past the entry gates and there is no charge. The lake does have water skiers, so winter and weekdays are quieter. Entire circuit of lake about 5 miles.
Water quality is low.
Lake Borundi Foothills Park, Palo Alto. Must be with a Palo Alto resident for entry to park. Small lake, good for a family outting, with frogs, redwing blackbirds, and a small island. Very few people. Stevens Creek Reservoir, Cupertino.