A "Wolf's Call' is a navy slang for active sonar alarm. That means the submarine is detected and targeted. Active sonars sound very different to the human ear based on the transmission frequency. Low-frequency sonars are a very deep, like a moaning bass. Medium frequency sonars are like some synth doing an imitation of whale songs. High frequency sonars are strident and creepy like "howlings."
ALFOST, the character played by Mathieu Kassovitz, is an acronym for "Amiral en charge de La Force Océanique et STratégique" (Admiral in charge of oceanic and strategic force), comparable to COMSUBFOR (Commandant, Submarine Force) in the US Navy.
The Wolf's Call was inspired by director Antonin Baudry's real-life experiences as a diplomat, advisor and speechwriter for France's former Foreign Minister, Dominique de Villepin. Baudry spent a month observing a real French military submarine to make the film credible.
During a scene, Omar Sy can be seen driving a car with a small dinosaur toy placed on the dashboard. Sy also appears in Jurassic World - O Mundo dos Dinossauros (2015), which is a film about a dinosaur park.