If you live in the north or south Bay Area, you don't have to trek all the way to the east bay to swim. Here are a few more lakes for summer swimming.
1. Lake Lagunitas. This Corte Madera lake is a favorite with Marin County families. And rightly so. You can hike it, bike it, or fish it.
2. Bass Lake. Many Marinites swim in the buff in this hike in lake, but don't let that freak you out. The lake is hugged by a lovely meadow, ideal for lazing in the sun with a picnic. If you are inspired, you can hike all the way to Bolinas beach to see a waterfall in spring.
3. Almaden Lake Park. This is the only lake in the San Jose area. So you can excuse the crowds, especially in the heat of summer.
See my other posts on Bay Area lakes and Northern California lakes for more information.