To what element of life is the metaphor of "chum" connected in the poem of the same name?

The poem entitled "Chum" likens young girls of eight and nine years old to the chum that is used to attract sharks. Anderson describes innocent and sweet girls who are just trying to cool off on a hot day at the neighborhood pool. She goes on to depict the cruel and violent treatment the girls experience in the deeper end of the pool before they realize that they must stay in the shallower water. This is because the preteen boys converge on the young girls, grabbing the girls' crotches and twisting their barely-there breasts, as the lifeguards ignore the behavior and do nothing.