I watch this movie many times due to the overwhelming of patriotism I didn't notice one thing while in the movie when S 21 was approaching the hills Lt.commander Arjun noticed the graph, on that time why sonar not detected the mine. After hitted by mine to the sea bed then recovered from sea bed Lt. Commander Arjun ask sonar to check the other mines. I can't understand that part, will any of them explain this to me. JAIHIND🇮🇳.