Bees
Honeybees are rather common in the area, especially during Spring and Summer (Burris, 2008). They are known to occasionally fly in swarms. If stung by a bee, you should see a lifeguard. If an allergic reaction occurs as a result of the sting, seek medical treatment immediately.
Reference
Burris, A. (2008). AROUND THE CORNER: Bees start to invade as summer sizzles on. The Orange County Register. Retrieved August 10, 2009 from http://www.ocregister.com/articles/bees-check-find-2081123-calls-bee