Japanese culture uses water for purification, and Christian culture for baptism. I think it is a representation of both cultures, which respect water as a source of living beings.
Water knows no border!
In Japanese culture, water plays an important role at big moments in people’s life as medium between life and death. Starting from the first bathing, the water is used for many ceremonies such as when visiting Shrines, New Year’s special drink, offerings for gods in temples, shrines, or houses, and so on.
People would exchange a glass of water instead of drinks when they apart, or give water at people’s death bed for the departure.
Water purifies itself, and gives lives to other living creatures at the same time. Therefore, water is sacred.
Spring is around the corner. There is a famous ritual called Omizu-tori, or receiving water, which announce spring. It is believed that the ritual gives the country a new life; that is a proof of Japan being a land of water.