The history of Our Lady's Tank is deeply intertwined with the legend of the apparition of Mother Mary in Velankanni. According to local lore, a shepherd boy was carrying milk to a nearby town when Mother Mary appeared to him near the pond. She asked him for milk for her child. After fulfilling her request, the boy continued his journey, and upon reaching his destination, he discovered that the container was still full of milk. This miraculous event led to the recognition of the pond as a sacred site. Over time, a shrine was built near the tank, and it became an integral part of the Velankanni pilgrimage. The tank continues to be a focal point for devotees seeking blessings and healing.