Polyurethane Pond Waterproofing A polyurethane pond sealer ideal for fish ponds, water features, planter boxes and water troughs. Non-toxic - fish and plant friendly. Flexible, seamless and durable. Suitable for permanent immersion in water. Ready to use and easy to apply. Single component solution so there is no measuring or mixing - simply brush on. Excellent adhesion, especially when used with Duram Duraprime. Does not taint water or food. Odourless when cured. A polyurethane pond sealer ideal for fish ponds, water features, planter boxes and water troughs.