Yes, I mean keeping external water out. Specifically for me, it would be for hiking through muddy marshy areas. And, it's not just to keep my feet dry but also to keep the dirt and grit out that the water carries with it. I have seen VB socks similar to the ones you linked, but I'd prefer a cheap solution if it works.
Seems like a decent compromise to only wear the bags around camp. I've been keeping my wet socks on until bedtime and only then have I changed into my dry socks. It sure would be nice to have dry feet around camp though.