If you play along with manoeuvre, go here
From Create Your Own Story
You follow him along by going deep too. Borodin has prepared the countermeasures for launch just in case a torpedo comes.
The other submarine is just too fast. It is behind your propellers in no time and is preparing to shoot. You are about 1 km ahead and the other ship releases a torpedo that is instantly active. It looks like it has acquired and it fast on your tail with less than 15 seconds to spare!