There be monsters

It always gives me a thrill when I spot Chichester Harbour's resident seals, who occasionally swim round the boat, popping their heads out of the water to take a look in, I like to think, a friendly sort of way.
But that is nothing compared to this, taken off Santa Cruz on the California coast. I think that it might cause me some alarm, not to mention an underwear crisis. It is the star picture on the website of the Santa Cruz Rowing Club (thanks to neversealand for the headsup).