Half moon bay is home to the world renowned Mavericks surfing competition.  In 2008  the event was held on January 12th.  The event is held annually and the date depends on the wave conditions.  They usually only give 24 hour notice of the event.

Definitely worth the trip to come and see it if you are in California when the event is announced.  We drove down Saturday morning from San Francisco.  Just go south on Hwy 1.  The drive only took about an hour and a half.

The best area to view the surfers (other than from a boat) is from the cliffs on the north side of Half Moon Bay.  There is tons of parking at the airport but it is a bit of a hike to the cliffs.  Those in the know bring a bike binoculars and snacks.