Master Lin helped me find these words in Taiwan, To be like water in all things, is the second most common taichi instruction that I receive, the first being of course to relax!
The indescribable aspects of Taichi are often alluded to with the properties of water. It has no shape but can take any shape, its softness causes the most hard to yield and many other beautiful references.
If you would like to see this beautiful power expressed in a different martial arts, please see this link. 10th Duan Judo Master