Sorry guys, definitely a dolphin. The dorsal fin and the orientation of the tail give it away. This happens fairly often when I have surfed in San Diego....
Good call kppolo: http://snopes.com/photos/surfer.asp Scared the crap out of me though. BTW, while I find snopes trustworthy, this sentence "A subsequent photograph of the animal taken later in the day demonstrates conclusively that it was in fact a dolphin:" is ridiculous.
It's a dolphin. I've surfed with dolphins from Old Man's below Trestles and just for good measure, a whale chillin' in the background as I was less than a board-length from 2 dolphins in Malibu. Touching Manta Rays off Isla Vista/Goleta, seeing them in Santa Barbara and too close for comfort with the occasional shark just waiting for the right time to home in on sea lions in Cayucos, Morro Bay and Pismo. Very cool - they all get close to shore if there's hotties wearing clear thongs to check out, and take years of stress off. Unless it's a shark, of course. Incidentally, if you look in the background of the pic, you'll see wave after wave lining up like corduroy - looks like he was about 100 yards out at 3rd point on a day with a nice S/SW swell.
The dolphins will come into the breakers when a school of fish is in the waves, or when they feel like "playing" I guess. They come into the sets and swim along the inside of the waves and move down the line as they go...much like surfing. Also, The dorsalfin of a shark is rarely that nicely curved in the back. The tailfin is horizontal although it is not so obvious on this picture. If it was vertical it would be as clear as the dorsal fin on the picture. There should also be a second dorsal fin between the tail and the visible fin. The pectoral fins are very obvious with sharks and should be seen on the picture whereas with dolphins these are more flexible and are often more under there bodies as on this picture. The pointed snout is also a good indication. If someone can show a clear picture of any kind of shark which has similar proportions I would love to see it. http://www.surfshooter.com/DolphinInfo.html