The Angel's Command

The Angel's Command is a book written by Brian Jacques (writer of the popular children's series "Redwall"), and the sequel to "Castaways of the Flying Dutchman". It follows the adventures of an immortal boy and his dog as they face pirates and other dangers from the high seas to the mountains.
The "Castaways of the Flying Dutchman" trilogy is based on the legend of the "Flying Dutchman". It tells of how a young boy and his dog managed to escape what happened to the "Flying Dutchman". They were given the ability to live forever, speak in any language, and talk to each other with their thoughts. Ben, the boy, and Ned, the dog, are sent to help those in need. 
In "The Angel's Command", they have a lot of adventures, including meeting a French buccaneer and a girl named Karay who's a thief. "The Angel's Command" was followed by a sequel in 2006 called "Voyage of Slaves".