What makes Muck Boots so great? Simple - it’s all in the design. All Muck Boots are 100% waterproof, keeping feet warm, dry and protected in harsh weather and messy working conditions. The secret – the exclusive, self-insulating, waterproof, and very comfortable CR-foam shell construction. The CR-foam bootie material acts as a “neutral medium” between inside and outside temperatures, keeping foot and lower leg warm and protected in cold and wet conditions.