What is the purpose of sprinkling water at the beginning of a ceremony?
When the person who is to perform the religious ceremony is seated the priest sprinkles water on him and chants the following mantra:
One may be in a pure or an impure state. In any situation if one remembers Lord Vishnu, one becomes pure.
Normally everyone who joins in a religious ceremony does so after a bath. After chanting the mantra and sprinkling water, the performer's attention is immediately focused on the ceremony. Sprinkling water is symbolic of purity.
Lord Vishnu was sleeping on Kshirsagar (the ocean). A lotus bloomed from his navel. Brahma emerged from this flower and created the world. This means we too emerged from water. The sprinkling of water reminds us of our origins.
The lotus comes out of water, but is impervious to water. This makes it symbolic of detachment. Sprinkling of water again symbolizes that the person performing the ceremony should learn to live a detached life.