this clip is a cracker for sure - I've had a link to it on my old homepage for a few years now and it's always worth a look, just for the pant-crapping horror of it!
The "Quiksilver Big Wave Invitational in Memory of Eddie Aikau" runs when the waves are at least 20 feet within a 2 -3 month period. In it's 22 year history it has run only 7 times. I saw a documentary a few years ago about it and it was mesmerizing!
I'm not sure where this one is from but they get pretty big in Hawaii and there are certain spots farther away from shore where it actually breaks in "open water" ... that's why they have the jet skis take them out.