Lying in the Deep by Diana Urban is a YA thriller that I (at age 54) found very entertaining! Jade, recently dumped by her boyfriend Silas has boarded a ship to tour 11 countries in 4 months, only to find Silas is on board too with his girlfriend, her former best friend Lainey. They're off to an awkward, stressful start when Lainey's cabin is discovered with her blood... LOTS of blood, leading out to the balcony where she must have gone overboard as she's not found anywhere on the ship. The others believe Jade had to have murdered her as she's the betrayed BFF, so Jade needs to figure out who killed Lainey and prove her innocence... then the bodies start adding up! Is there a serial killer on board? Does it have anything to do with Lainey's wealthy father's pharmaceutical company and his shady dealings? What's up with the older passenger the kids call Sketchy Bob? Can Jade trust the brooding, handsome young man named Felix? Can she trust anyone on this ship? Full of twists, this was a really fun tale of travel, lies, deceit and betrayal. I recommend this for teens and up.