Why is Marin given seashells by the people who remember her mother in the San Francisco community in the novel, We Are Okay?

In LaCour’s novel, seashells symbolize respect and empathy for Marin. In Marin’s San Francisco community, many remember her mother who died due to a surfing accident when Marin was just a baby; however, Marin’s memories concerning her mother are essentially nonexistent. Therefore those who remember Marin’s mother give Marin seashells when they see her. This gesture is meant to act as an expression of love and warm remembrance.