;)It's just a dolphin{at least that is what I'd tell myself}
Apparently the guy saw it fleetingly and assumed it was something harmless. It was only when his friend who took the picture (don't know what from, as it was two miles out to sea - a high and very stable boat, or maybe a helicopter!) pointed out that it was a great white that he realised how lucky he'd been!
Although these creatures are much maligned. Some friends of mine were diving a couple of years ago on the Protea Banks, off Natal in South Africa. Just normal unprotected scuba, when a juvenile great white came up close, had a good look, then stayed with them for over 5 minutes. Juvenile, but still probably 15ft long. Apparently they all turned as a man to watch this shark the whole time it was with them, and for quite some time afterwards. I believe they decided to end their dive prematurely!