Great White Shark Cage Diving?

So, my little brother wants me to take him cage diving off the coast of California on one of these Farallon Islands tours. I've been hemming and hawing because I have never really wanted to swim in chum infested waters while trying to catch a glimpse of a Great White in the water with me at the same time. Don't get me wrong, I love to see sharks while diving and have in the Channel Islands and in the Philippines, but these were 1. not Great Whites and 2. in their natural environment. Plus, I'm still torn on the "controversy" of cage diving and chumming in general. Is this a good idea? What say you?