Great for Shallow Work, but has Cons
I bought this for my Canon 50D and 24-105L Lens Combo. I use it snorkeling and SCUBA diving and have taken the unit down to 75 feet. It has not leaked. This is a good thing. You, however, get what you pay for (and that is not a bad thing). I did not want to spend $1,600 on hard housing so I picked this up. It works great in shallow water. You need to fill unit with air prior to submerging, which requires you to add weight. I bought the weight that comes as an accessory yet still clip on 3 pounds for a total of 7 pounds weight. That causes some serious awkwardness wielding the camera. You need to get used to it. As the air compresses, clip on weights are good because you can remove it from the unit at depth. I had difficulty using the unit beyond 60 feet. The air inside compresses so much that it was very difficult to use the controls (think vacuum seal). I have also found that the shoe mount flash is just too close to the lens that I shoot mostly with flash off, otherwise every particle in the water is reflected in flash (not a problem in really clear water). Overall, I like it and am satisfied, but I know that once I start diving more I will buy a better housing. If you can't afford a pro housing yet want to take your SLR underwater do not be afraid to buy this unit, just realize there are limitations.
Ewa-Marine Underwater Housing
Great for shallow depth work with MkII and 580ex.. also used 24mm 1.4 with no additional light and got good results.
best to set ASA and other preferences before putting in case... review buttons work pretty well and wheel works ok... I feel safer with this bag than a hard case ... have never gone below 6'... USM lenses work better than external focus.. a rubber band can keep front glass flat against lens housing...