In T.S. Eliot's the Wasteland, water represents both rebirth and death, and colors each theme with a degree of wistfulness. Spring rain is one of the "cruel" aspects of the month of April, a vital component of the rebirth of the seasons, yet harsh in the way it stirs life anew.
Eliot refers to water indirectly later in referencing the Hyacinth garden, saying "Your arms full, and you hair wet... I was neither living nor dead...
In this case water acts as a component of a memory, colored with a strong degree of melancholy. All the elements of this moment worked to move the narrator of the poem into a limbo, a temporary nether realm of neither life nor death.
In reference to the Tarot reader, and "Fear death by water" the mention is made ironically, as Eliot uses the starkness of the prediction to undermine the validity of the fortune teller. Essentially all people can fear death by water at some point in life.