Well my tactics was something like this... the moment you hear "torpedo in the water" warning, (assuming it's a submarine or surface ship launched weapon) turn the sub on the course opposite to the declared torpedo bearing, start to retract the towed array sensor, and order "ahead flank", all of that in a quick sequence.
If you can, try to identify torpedo type!
After some 40 - 50 seconds of sweating, (assuming it was not Shkval torpedo type, in which case you will have the time to blink twice and die with a stupid expression on your face
)... wiggle the sub a little bit i.e. change course to the port or starboard by ten degrees few times... because your at ahead flank you are practically blind and deaf, BUT!
IF the torpedo is after you, you will hear a sequence of rapid sharp and loud pings, and then is time to drop active countermeasures... If you can't hear anything, try the passive countermeasure first, but remember, passive ones are like bread crumbs you are leaving behind you!
If all goes well you will hear sonar man "loud explosion bearing 180" or something close to that bearing... if not... well... MAYBE you will have the time to reload countermeasure tubes, IF the torpedo was launched from bigger distance... otherwise you are dead!