In Operation Hadal, the sole military-themed film to compete in the lucrative Spring Festival holiday market, the biggest star isn't an award-winning actor or a household celebrity — it's a 120-meter-long nuclear submarine.

As the first feature-length film to revolve around deep-sea submarine warfare in the century-long history of Chinese cinema, the film, under the helm of Hong Kong director Dante Lam, has captured widespread attention from military enthusiasts.

With a runtime of 146 minutes, the movie has grossed 323 million yuan ($44.3 million) at the box office since its domestic debut on Jan 29, the first day of the Year of the Snake.