Yeah, I was inherently suspicious of the variable magnification ones, but they do seem to get positive reviews, so I figured I'd ask.

The Pentax and Nikon are not waterproof, although Pentax evidently makes a waterproof model for around the same price.

The Leupold and Vortex are both listed as waterproof.

The Pentax kind of intrigues me, but it seems to be by far the least widely available.