Video Rain covers for hurricane chasing

Two year on the trot I have ruined camera equipment during hurricanes ~ This year I want to protect (as far as I can) a canon SLR 10D with 77mm lens and a soon to be delivered Sony FX1 (lens size unknown)

I have seen the water proof bags ~ does any one have any experience of these and how on earth do you operate the camera with the bag around it ??

I also understand that divers use these bags and pack the inside with the silica gel …