Shui Jing, also called Water Crystal, is on the Kidney channel 2 cun below the apex of the medial malleolus. This point is often used with Shui Xiang (Water Image - 66.14) and Shui Xian (Water Sprite - 66.15).
To locate this point, find the hiatus of the medial malleolus and measure 2 cun distal to it. This point is on the calcaneal bone.