Water is the substance the Tarot cannot stop drawing. It pools, falls, reflects, and crosses through more cards than any other element, and almost never as scenery. Where it appears, it marks the unconscious — the part of a life that moves on its own, beneath the reach of the will.
The deck spends a remarkable amount of its imagery on figures standing next to water who have not yet entered it. The High Priestess at her pool. The Two of Swords with the sea behind the blindfold. This is not an accident of composition. It is the deck naming its most common failure: the figure who decides to stay on land.
To read water is to ask one question before any meaning: where does the figure stand in relation to it — on the shore, in a boat, one foot in, fully immersed? The answer is usually the reading.