When Dante Lam saw a six-minute clip of a documentary about marine rescue and salvage in 2014, the Hong Kong director－best known for his action blockbusters－was instantly hooked.

In the footage produced by China Rescue and Salvage, a national force administrated by the Ministry of Transport, Lam saw three rescuers descending down a steel rope hanging out of a helicopter hovering over the raging sea.

Facing off against turbulent waves, the rescuers risked their lives to save the screaming passengers and crew trapped on the hull of a sinking cargo ship, two-thirds of which was already submerged underwater.

"I watched the clip over and over again. It was extremely dangerous and I really admired the courage of the rescuers. It felt so thrilling to see the destructive power of nature, which I realized I could easily paint as the ultimate 'villain' in a movie," Lam says in an interview with China Daily.

His previous directorial forays, 2016's Operation Mekong and 2018's Operation Red Sea, yielded box office hauls of 1.19 billion yuan ($172 million) and 3.65 billion yuan, respectively, with the latter reaching the top of the box office charts. Lam is, to date, the highest-grossing Hong Kong director in Chinese-language cinema.