La Petite Baleen for swim lessons. With locations in San Francisco, San Bruno and Half Moon Bay, they have several places to choose from. Groupon is offering a special deal today, where you can get one month's worth of lessons for $40. It's normally $86 in San Francisco (and $81 for the other locations).
From what I gather on the website, that price includes one half-hour lesson weekly for four weeks. You can read about their classes here. And you won't need to pay the normal $25 registration fee.
To get the deal or learn more about it, click this Groupon link. The deal is good today only. It should take you to the San Francisco page, where the deal is located. If it takes you to another city's page, just go to the top where it says "visit more cities" and click on that. Find San Francisco and click on it.
Small print: You can buy 3 of these Groupons for your family swim lessons at La Petite Balleen, though only one per child. You may purchase them as gifts. You must be a new customer. You must use them by December.
If you purchase this Groupon using my link, Frisco Kids will get a small credit toward a future Groupon purchase. It will cost you nothing extra and you will be supporting this wonderful website which is brought to you at no cost.