Before GPS, They Had the Genglubu

No GPS. No weather forecasts. For generations, Hainan fishermen relied on a handwritten manual to navigate reefs, avoid danger and find their way home. Known as the Genglubu, it was an unreadable code to outsiders – but to fishermen, it was the most valuable thing on board. Genglubu: Charting the South China Sea. Premieres July 9 on CGTN.