In the summer of 1944, at the height of World War Two, a treacherous stretch of water in the Philippines claimed the lives of more than 150 American sailors, lost when the U.S.S. Flier and the U.S.S. Robalo sank. Neither sub has been found, and the exact cause of their sinking is unclear. Can the Dive Detectives unlock the mysteries?

Their search leads the Dive Detectives into dangerous waters—the territory of sharks and ruthless pirates. But the Team is protected by armed Coast Guard officers and assisted by dramatic clues. The deathbed revelations of a retired member of the U.S. Navy help launch the search for the Robalo. The Team is intrigued by leads that include a mysterious sketch appearing to pinpoint that sub’s location.

The hunt for the Flier is driven by an eyewitness account from a survivor, Al Jacobsen, committed to tape before he died. Al’s son joins the Team in the hope of fulfilling his father’s life-long mission—locating the lost vessel.

Cross-referencing Al’s information with U.S. Navy inquiries and the results of cutting-edge side-scan sonar, the Dive Detectives investigate the locations of the downed subs. Their quest unites them with local “hookah” divers, who dive deep using only a hose and air compressor. They also get a taste of what it was like for the sub’s handful of survivors, who escaped their downed sub and fled the enemy via an 18-hour swim and a 5-day journey across tiny islands to safety.

It’s a journey of discovery as the Dive Detectives follow the clues across a remote and beautiful area of the Philippines, and what the Team discovers in the bone-crushing depths of the Balabac Strait ranks among the greatest find of their careers.