Book I read in middle school

Okay the book was about a boy who was leaving the country with his mother. Father couldn't leave because of his job or something. They got on a boat to leave and it was maybe blown up by a submarine or something. The boy lives and ends up on an island with a slave that was also on the boat. They end up living on the island for a while, at least months if not years. During a hurricane the slave guy dies protecting the kid (they were tied up to a tree together I think). The boy then has to continue living on his own. Eventually he is found and rescued.

Please help, I've googled different things and can't figure out what book this is. I wanted my little brother to read it because I remember it being a good book.