system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it such a difficult task to locate and rescue a malfunctioning submarine at sea and why can't all the sailors escape safely via the torpedo tubes in pressure suits?

These questions came to my mind in light of the recent San Juan disaster.
gpt
The ocean is *big*. Incredibly big. And huge swaths of the sea floor haven't been mapped. You're talking thousands upon thousands of square miles to look through, except you can't just look. You have to use sonar instead. Is that roundish bump that showed up on the sonar the nose of a submarine? Or is it just a roundish rocky bump on the bottom of the sea floor? Is the sub not in this area, or was it just in the shadow of a rocky underwater ledge so your sonar couldn't hit it? Is the submarine even still in one piece, or is it in pieces? How many pieces? Did the pieces settle on the bottom together, or did an ocean current drag different sections miles apart before they hit the bottom?

Did the submarine continue on a straight course, or did it get caught in a current? Did the engines or props or rudder malfunction, so that it veered off course? When? By how far?

You're basically looking for a needle in a haystack after a storm blew your haystack all over the place and also you're not allowed to look for it, you just have to poke around with your finger until you find it, and also it could just as easily be in your neighbor's haystack.

There aren't pressure suits on board. You can't carry enough for every sailor, and it would be impractical and expensive to carry the right kinds, especially since at some of the depths a sunken sub would end up in, a suit wouldn't help you. There are hatches and small oxygen tanks and flotation devices to get you out, but you have to get to those. There's no guarantee that the sub isn't already flooded in the corridors between you and any of those things. Sure, you could open up the torpedo tubes, *if* you are close enough to them, *if* that room isn't already flooded, *if* you can get the tubes open, *if* the sub hasn't already sunk too deep for you to escape without help...