Last month Brett and I went up to Gainesville to do some water work for an At&T Olympics spot. I spent a day prepping and a day shooting Ryan Lochte in the Pool.
They ended up using a hand full of really cool shots from the Alexa at 60fps. They added a ton of CG fish and colored the heck out of it and made it look really, really nice.
The grip department had a tough job on this shoot. They had to black out an entire Olympic pool. Black rubber mat on the bottom (with vents for the drains and jets), black 20x's on the sides and a monster, two story black curtain on a construction crane. The curtain was (if I remember correctly) 80'x60'x15'. All hanging on a double stack truss rig with a black plastic top. The whole thing had to hold up in heavy wind and rain and be moveable so we could make it dark and then make it light depending on the shot. Really nice rig, my hat goes off to them.
I'm really happy with the final spot and look forward to doing more under water work in the future.