I really liked the setup of this one. I liked being on the boat. I liked the moments where every member of the boat was suspect. Except, it didn't feel like this nearly enough. There were efforts to lead us down stray paths, but I was never fully diverted. (And I am geographically challenged.) I never really felt the paranoia I wanted to feel with this. And the last 1/4 of the book had me scratching my head a bit. It just seemed a bit too convenient. And also less active. 
 Still, as a summer thriller this fits the bill.