[CALIBK12] Book title - help needed!

[Ann Green]

I have a student trying to remember a book that he read. 
Main character is a teen/young man who becomes invincible 
by selling his soul (or making a deal with ???). He 
recalled two incidents: first, the character realizes he 
is invincible when he accidently cuts himself at the 
dinner table; later, there is some kind of shark attack in 
the Caribbean.  Does this ring any bells?

Thanks!

Ann Green, Librarian
Cloverdale (CA) High School