Mary Margaret is a spunky ten-year-old girl with a tough mission. Her mother has asked her to accompany her recently widowed grandmother on a cruise to the Greek Islands. Mary Margaret wonders if she'll really be able to help her grandma get the rest, relaxation, and recuperation she needs, or if she'll just be in the way on this seniors-only cruise.
But in time Mary Margaret makes new friends, helps her grandmother say good-bye to Grandpa, and finally has a chance to fulfill her being-a-mermaid dream by joining in a beachside wedding dressed as a mermaid. Along the way she learns a little about the ancient world, a little more about herself, and a lot about delighting some grown-ups who need a red-headed mermaid in their lives. A smart and sensitive story told through the journal entries of a very precocious mermaid-in-training.