What does it mean when Norman says, "I am haunted by waters" in A River Runs Through It?

This quote appears at the end of A River Runs Through It, after Norman has spoken of the death of his brother, Paul, and of his old age, when he fishes alone (though some people warn him he shouldn't). Norman sees in the waters the remnants of history, as the rocks at the bottom of the river are from "the basement of time." Atop these rocks are "timeless raindrops," which are also ancient. Norman is haunted by waters, just as he is haunted by the ancient unanswerable questions, such as why he couldn't help his brother Paul in his suffering and why he couldn't prevent Paul's death. The waters remind Norman of the ancient sources of the river and rocks, and they also remind him of the eternal mysteries of the earth that make it hard for him to understand the ways of people, including his brother.