What significance do the glass bottles with ships inside have?

Susie and her
father had made the ships in a bottle together, and they are a reminder to him of her death.
Jack, Susie's father, looks at the snow globes and the bottles with ships inside as perfect
little worlds that are so fragile they can easily be destroyed. They symbolize how Jack's family
has been shattered by Susie's brutal murder by a serial killer. After Susie's death, the family
falls apart, and Jack is obsessed to find her killer. Susie's killer has destroyed Jack's
perfect little family, and there was nothing Jack could do to prevent it.