In '99 when I went on Splash Mountain, I had my camera in my fanny pack. I got soaked on SM so much so that I went into the bathroom and took of shirt and shorts to ring out water. my camera never got wet.
In Animal Kingdom, on the raft ride, they have a center area of the raft to put bags into, and I did put my fanny pack in there. It stayed dried. No problem.
Ziplock bags for your camera, weither storage or freezer should work fine. I use the to store everything in my fridge, and have never had a problem. (even when the fridge broke and left puddles, the bags floated)