The book read by Kay Kay Menon, "War as I knew it", is a collection of General George S. Patton memoriers from WW2. He died on December 21st 1945, before he could complete them.
Late Om Puri's charachter in the film is based on Indian Chief of Naval Staff during the '71 War, Admiral Nanda.
This is india's first submarine based war film
It is India's first underwater/war-at-sea film.
Menon, Daggubati and Pannu were all parts of "Baby" (2015), also based on India-Pakistan conflicts.