Chris Weitz talks about Roberts Stunts in "New Moon"

I also read that you had instructed Kristen to do that scene one way and then got a wet suit on and got into the water yourself and realized it was an impossible way to tackle it.

Rob had done this underwater work in one of the Harry Potter movies, so he was relatively comfortable doing things at the bottom of a pool. In order to get this shot right, we needed to get a top shot of Kristen as Bella sinking down in the ocean. The best way to do that is to have Kristen at the bottom of a 12-foot pool weighted down, just sort of floating there immobile. And Kristen was already expressing a bit of concern about deep water, and I told her, "12 feet isn't that deep!" [Laughs] I decided to go down there in a wet suit weighted down and I started to panic.

I thought, "Holy crap, this isn't fun at all!" and realized Rob actually had some guts and that the rest of us should really stay up towards the top of the pool. We adjusted it so we could make our shot sideways and it looks just the same as a top shot. And Kristen had a cold that day, so that was the last thing I was going to do — put someone with a cold at the bottom of a 12-foot pool with weights in their pockets. That didn't seem like a wise move.

Source via lion_lamb via pattinsonlife