I have StormSocks - a different brand, similar idea. They are much, much thinner than Sealskinz, so they fit into shoes easily. What I find is that they are good for a while, but little to nothing can stop water from coming down your leg and getting into your socks after an hour or two. The socks tend to hold in the water that comes in, so you swim a bit if you are out for a long time. (I had Sealskinz gloves for a little while and I hated them.... they were like wearing water balloons after a while.....) The Stormsocks are light and tight enough to not feel too bad even when soaked through and they are completely wind proof, which means they tend to keep warmth in.