The Arctic Shield boot insulators work great in my opinion. I can't say how they would work if your feet are wet. I think the key is to put them on before your feet get cold. Arctic Shield works with what they call RE-tain technology. Check out
www.arcticshield.com. Also I've seen how they demonstrate their boot covers. They pack your foot with the boot cover in a bucket full of dry ice for several minutes to prove that the boot insulators will retain and conserve heat loss.