Jaffna Keerimalai springs: underground freshwater karst aquifer and bathing etiquette?

Keerimalai Springs on the northern tip of the Jaffna peninsula features an ancient stone-masonry bathing pool situated directly on the shore of the Palk Strait. Despite sitting within 10 meters of breaking sea waves, the water inside the pond is completely fresh and crystal-clear. The spring discharges from an extensive subterranean karst aquifer system running through Miocene sedimentary limestone (the Jaffna limestone formation). The high hydrostatic pressure head of inland groundwater prevents seawater ingress, producing mineral-rich, therapeutic freshwater believed in Hindu tradition to cure skin ailments.