I checked out a number of books for my son, all 6th-grade reading level, and among them was Lloyd Alexander's The Marvelous Misadventures of Sebastian. 
Since my son chose another book to read first, I decided to read this one myself, and I'm glad I did because I enjoyed it very much. Sebastian is a young fiddler who works for Baron Purn-Hessel. Because of an accidental slight against a powerful nobleman, Sebastian loses his place at the Baron's estate and is forced to find his own way in the world. Sebastian's journeys bring him in contact with many characters, both good and evil, but the most important is Princess Isabel, who has run away to escape marrying a man she does not love. The story offers plenty of humor and adventure, and even a touch of magic to keep things interesting.
In the beginning of Demons of the Ocean, by Justin Somper, 14-year-old twins Connor and Grace Tempest's father dies. 
Their mother has never been a part of their lives. Since they don't like the two options for a new home they are left with, they take their fatehr's boat and head out to sea, only to be caught in a storm and thrown into the ocean. Grace is rescued by vampirates (vampires who live at sea), and Connor is rescued by the regular, swashbuckling kind of pirates. The story is told in alternating chapters about Grace and Connor's adventures aboard the two ships, which works well for creating suspense. Both kids make friends and start to feel at home but also yearn to find each other again.
This is a story about vampires, but only just. The vampires on Grace's ship are like the Cullens in Twilight. They are civilized and want no harm to come to her. Well, most of them, anyway. And the pirates on Connor's ship are not so much bloodthirsty as greedy for treasure. Still, this is one of those books you just don't want to put down, and I'm looking forward to reading the next two in the series.
I've always loved books about pirates and the ocean, and I've always been a mystery fan, so Ghost Ship, by German author Dietlof Reiche, was a lucky find for me. 
The story revolves around an 18th-century ship called the Storm Goddess that was lost at sea. One day the water disappears in the bay that used to be the Storm Goddess's home port. Shortly after that, the ship herself appears in the middle of the dry bay and people begin to hear mysterious sounds that seem to be coming from the ship.
Vicky, a 12-year-old girl who lives near the bay, is determined to discover the truth about the events of 230 years ago. Of course, since there is treasure involved, Vicky is not the only one who interested, and the plot thickens.
