An HDPE pond liner is a durable, flexible sheet made from high-density polyethylene, designed to prevent water loss from ponds and to protect the surrounding environment from contamination. The primary function of a pond liner sheet is to create a waterproof barrier, which is essential for both natural and artificial ponds. Whether you are constructing a garden pond, a wildlife habitat, or a larger water feature, using a pond liner is essential for maintaining water levels and ensuring a thriving ecosystem.