"I just got through watching reruns of the Eco-Challenge, and was wondering what those competitors (and us less adventurous hikers) can do for very wet, muddy, and slushy hiking conditions? How about Gore-Tex socks and some strips of duct tape around each calf to keep the water out?"
That's a good question, to which my first response is that those people you saw on TV don't worry about wet feet. They just live with it.
But what about ordinary mortals who want to keep their feet dry? Certainly, Gore-Tex socks typically work pretty well. They already have a stretch band around the upper portion to prevent water from glugging down into the sock proper. There's also a material called SealSkinz, first developed by DuPont, that is made into an excellent waterproof sock sold under the SealSkinz brand. It's about $30 for a pair, depending on the model.
The trouble with either solution is that your boots are still apt to get soaked, making them cold and uncomfortable. So a waterproof sock, except when wearing really leaky shoes such as trail runners, is no replacement for wearing a good-quality, waterproof bootand keeping that boot treated for water-repellency with something such as Nikwax Boot Treatment. Also, I suggest wearing a gaiter, such as Outdoor Research's venerable Crocodiles. These are designed to keep snow out of a boot, but also help keep the boot uppers dry and water from sneaking in the top of the boot. I've actually waded streams with Crocodiles, and if you move fast you can usually cross before anything leaks through the seams.