Thank you for validating my point. I know you inadvertently did so. Point being, it is extremely difficult to detect something in vast deep ocean.
Exactly - a good reason why Pakistan should have shut up & sit quietly when TTP blew up your P-3C Orions instead of requesting US for replacements...after all, they are just there to suck up Pakistani taxpayers money to fuel & maintain them, and they would be totally useless in detecting any Indian submarine in IOR.
OR...you can read my next para to hopefully install some sense in your brain OS...
If it was a Pakistani submarine, I would say good luck to your P-8 and whatever!
...if it was a Pakistani submarine...
> It would be throwing off a range of sound, hydrocarbon, magnetic anomalies, radio and other EM emissions. All of which can be detected & tracked by onboard equipment on the P-8I.
> It would need to come up for air from time to time. Crashed planes don't do that to the best of my knowledge. I suppose you will now jump up & down about AIP. So let me explain that while it does extend the amount of time you can stay underwater, it is still a finite amount of energy, and while using which your speed cannot usually exceed 4-6 knots...meaning you can't chase ships anymore, and cannot get out of sight of MPAs fast enough.
Unless....you seat your submarine on the sea floor. All equipment off and the super-mutant crew maintaining pin-drop silence and able to survive without oxygen for days & days. Then, it would be almost equally difficult to detect as a crashed plane (I said almost because that much hulk of metal still produces a distinctive magnetic signature). But it wouldn't matter in this case because at that point you would have become totally combat-ineffective.
As good as sunk.
So in short, it would be the PN SSK that you should be wishing your good luck on. It will seriously need it.
