Stowaway — Constance Leonard

On what has to be a perfect cruise, sailing around the Bahamas in convoy with Pete Sturtevant and his important charter passengers, Tracy James discovers something even worse than a rat aboard the Kitten Too: Tessa, a small, terrified human stowaway, who bites but does not speak English! The little girl cannot explain what has happened to her family, nor warn Tracy about the ruthless men who, like the coral reefs just under the surface, make these beautiful waters dangerous.