I once read a great article on the history of the FF.
If memory serves me right, the French Naval Forces had issued a request to bid to several manufacturers to produce a divers watch for their new squadron that would perform underwater diving missions.
Virtually not a single manufacturer was willing to engage in this challenge and declined.
Blancpain’s owner at that time was an avid amateur diver and he was the only one to respond which led to the FF, the very first true divers watch (yes ahead of Rolex).