those water proof bags suck when it comes to operational capabilities though, you can press buttons in but cant spin things very well (especially the canon wheel on the back) and they are a PITA to zoom with.
Canon 40D with Canon 100-400 f4-5.6
I made this a while back and use it every time I am off to the beach. water resistant (for when your mate wanna look at the photo) and stops everything else from getting in. clear for the LCD displays and thin/loose enough material to operate all controls.
only downside is that the neck strap is no good but with that much glass a monopod is the only way forward anyway. entry opening on base allows the tripod thread to be accesed.
good for a 77mm to 60mm lens diameter and all filters, hoods etc work fine as the end protudes through the elasticated end. (UV to protect front element)
james