Water, shui, is one of the five phases of the Wu Xing, and like the others it is a phase in a dynamic cycle rather than a material element in the Greek sense. Water is associated with winter, the north, the colour black, the planet Mercury and the quality of maximum yin, stillness, depth, downward movement, and the potential held in reserve. In the generating cycle water is produced by metal and gives rise to wood (water nourishes plants); in the controlling cycle water is dammed and absorbed by earth and itself quenches fire.
In Chinese medicine water governs the kidneys and bladder, the emotion of fear, the ear and the bones, and it stores the jing, the essence held to be the deepest reserve of vitality. Water's symbolism is of depth, wisdom, the hidden and the stored, the deep pool and the winter earth holding the seed, and of the yin extreme of the cycle, the point of greatest stillness and inwardness from which, as the year turns, the upward wood phase of spring will emerge.
Sources Science and Civilisation in China, Volume 2: History of Scientific ThoughtJoseph Needham with Huangdi Neijing (The Yellow Emperor's Inner Classic)Traditionally attributed to Huangdi; actual authorship unknown