What are some good children's books about ships?

I'm trying to put together a thematic unit centered on ships and need more books for my literature list. Fiction books don't need to be about ships, but I would prefer that a significant amount of the book is spent on a ship - enough that readers get a good sampling of nautical terms. The only books I currently have down are The True Confessions of Charlotte Doyle by Avi and The Wanderer by Sharon Creech (books may be either historical or contemporary fiction). I would also like some well-written, engaging non-fiction books. Some books involving pirates would be fine, but I don't want them to be the majority of the list. Thanks!