SealSkinz
They allow a child with, for example, a below knee cast to play on damp sand on the beach. The Sealskinz is waterproof up to the cuff at the top and also breathable. This allows a child to use it when outdoors, keeping the plaster clean and dry without the fear of damage to the cast.
The SealSkinz sock will stretch over the cast and can be pulled up to well above the knee. The top is a knitted cuff which is not waterproof but dirt and dust resistant and will prevent grit etc from falling into the cast
Sealskinz Material
Outer lining: 91% Nylon, 9% Elastane.
Membrane: Hydrophilic membrane.
Inner lining: 35% Merino wool, 34% Acrylic, 28% Polyester, 2% Elastodiene, 1% Elastane
Available for kids of 3 to 13 years.