Water represents mind's continuity and adaptability. It also symbolizes the fluidity of things, and cohesion; that which brings things together.
In Buddhism, water is one of the most common offerings. In Tibetan tradition, water bowls are offered to represent the seven-branch offerings;

1. Prostration, the antidote to pride
2. Offering, the antidote to avarice
3. Confession, the antidote to aggression
4. Rejoicing, the antidote to jealousy
5. Requesting to turn the wheel of Dharma, the antidote to ignorance
6. Requesting not to pass into paranirvana, the antidote to wrong views
7. Dedication of merit, the antidote to doubts

These seven offerings incorporate the accumulation of merit and purifying negative actions. Accumulating merit, we purify negativity: Purifying negativity, we accumulate merit; and so we can awaken into our true nature.

The Masters tell us that building a temple is the most profound way of accumulating merit and purifying negativity. We can accomplish this for ourselves and others, by sponsoring the water element of the temple.