The new movie is a follow-up to Lam's action-packed Operation Red Sea, loosely based on China's evacuation of stranded citizens from Yemen during its 2015 civil war. Amassing 3.65 billion yuan in ticket sales, Operation Red Sea became the highest-grossing film of 2018.

Reprising some stars who play members of the Jiaolong Squad, an elite unit of the Chinese People's Liberation Army Navy, the film fictionalizes a new threat that jeopardizes national security. Set in the near future, the Chinese navy intercepts crucial intelligence — a powerful submarine conspiring in a top-secret military operation targeting cities along China's southeastern coast.