Well, you wonder, how dangerous could the "graveyard" be if Clark survived it solo for 15 years? Then word of Mavericks gets around, and legendary surfers from Hawaii's North Shore come to visit. One of the sport's champions, Mark Foo, is killed after wiping out on a medium wave. One theory is that the tether to his board got caught on rocks and he drowned. Another surfer thinks he felt or sensed somebody under the water who shouldn't have been there. Exactly one year later, during a memorial to Foo, another surfer is drowned. The documentary "Riding Giants" shows surfers gathered to discus...