Yesterday I was shooting video from the end of a jetty in Newport Beach CA. I was orbiting a sailboat at approx. 300 feet of altitude. I was NOT in a no fly zone. I heard a helicopter approaching from behind and when I turned and looked it was immediately obvious that there was going to be collision. I switched to sport mode and got the heck out of the way just in time. As it passed all I could see was that it was military and flying very low. I was under the impression that they are required to stay above 500 ft. Am I wrong.