screengrab from CBS5NewsWingit, a Corsair F-27 Trimaran, capsized and three crew members were rescued near the Golden Gate bridge this afternoon. There is some interesting footage of the rescue on the local CBS affiliate's web site.
Good news is that nobody was reportedly hurt.
The trimaran is owned by Ray Wells and is raced out of Alameda. They've won several races over the years and are out on the bay a lot. We've seen them out many times.
It's pretty unusual for a multihull boat to go over, but when it does, it stays that way. It's unclear from the video what happened but the retractable keel is not showing. It may have broken off or is more likely back up inside the hull.
The boat is a popular trailerable trimaran that has foldable amas (outriggers).
For more about the boat and it's racing history check out the Bay Area Multihull Associations website