Water is the symbol of Tao, the Way.
The Dao De Jing (chapter 8) describes it as follows:
The highest good is like that of water.
The goodness of water is that it benefits the ten thousand creatures*;
yet itself does not scramble, but is content with the places that all men disdain.
It is this that makes water so near to the Way.
And if men think the groud the best place for building a house upon,
If among thoughts they value those that are profound,
If in friendship they value gentleness,
In words, truth; in government, good order;
In deeds, effectiveness; In action, timeliness --
In each case it is because they prefer what does not lead to strife,
And therefore does not go amiss.
* 'Ten thousand creatures' refers to everything that exists, a holistic, pluriform, ecological view of the universe.
老子, 道德經, 第八章