Horse pond

A horse pond is a body of water used, and generally created, for the welfare of horses. Horses could drink and also have their legs washed in these ponds. They are less common in the age of powered transport.
Construction.
When a horse pond was constructed in well-drained soil, and not supplied by a brook, it was lined with puddling, about 6-7 inches thick, constructed of clay and lime, rammed or trampled home. The lime was to prevent worms burrowing through the clay and making it porous. Over the puddling a causeway of tone and sand is laid, to protect the puddling form the horses' hooves.
Horse ponds, especially by roads, were often designed so that the horses, and their vehicle, could be driven in one end and out the other. Typically the water would rise no higher than the horses' knees.