A few years ago my wife and I were kayaking in Monterey Bay when I noticed the Sea Lions playing Frisbee (no joke). When we paddled over to investigate it turned out that the "Frisbees" were actually juvenile Mola mola! They were about 20" in diameter and probably weighed at least ten pounds. Several of them were still alive, but pretty beat up. It was pretty sad, but also an incredibly cool thing to witness.
I asked a biologist about it at the aquarium and he said that they are found in the bay on an infrequent basis and gave me a web site to report the sighting to.