Dominick has a dramatic relationship with water. As a teenager, he runs into the nearby river twice: once after Ray throws pickle jars and Thomas cuts his foot, and again after the cops bust him and Leo for marijuana possession. "I was trying to wash myself clean of everything" (22.252), he says. Thomas later echoes this sentiment when he asks Dominick to bring him some of the same river water because he's "unclean" (26.110). Water, then, is a symbol for cleansing, for fresh starts, for washing away trouble.
Later on, though, Dominick drinks beer by water as an adult and drops the beer bottle "into the rushing river" (26.170). When he does so, we can recognize a disinterest in being cleansed, in fixing what's broken in his life. He shows disregard for the water, which in turn, lets us know that he's not in such a great spot personally.
Additionally, despite its cleaning connotations, water imagery is also often associated with not being able to breathe. The first time Dominick dives in, for instance, he stays under so long he thinks he's "going to drown" (17.279), and when Dominick considers suicide, he says he wants to "take the damn water into [his] lungs" (30.316). Instead of cleansing or renewal, then, here water expresses feeling overwhelmed.
Dr. Patel puts things into perspective when she says, "Life is a river" (36.110). In other words, it's full of good things and bad. As for the bad, both Ralph Drinkwater's sister and Thomas die at the waterfall near the river.
So which is it? Is it cleansing or suffocating? We guess it depends on just how deep you dive.