How does the water motif enter the narrative in relation to the death of Anderson’s mother?

When Anderson sees that her mother is having visions of her late family members, particularly her late sons who had never made it past the fifth month of her pregnancy, Anderson knows that it is time to let her mother go. She says at the end of the poem “lost boys” that she had known that it was time to release her mother “so she could cross the river home/to where the rest of the family was waiting” (275).