So let me see if I understand this. I dropped over $50 on a game where, even after going through the manual and every training mission, I can only survive the first single mission. Virtually every other one, even with difficulty set as easy as possible still results in getting my virtual self blown to pieces. Congrats developers, this is hands-down the most retarded game I have played - freeware or payware. No matter the settings or how cautiously you conduct operations, the enemy is all-seeing and invincible. That doesn't make it an entertaining "chess game", just a waste of my time and money because clearly in this version there's nothing to master except how creatively you can die. What a piece of s*** excuse for a game. And here I thought I had found something realistic that I would enjoy. Feel free to refund my money, GOG.

Which campaign are you on? I've avoided 1968 - non-wire-guided torpedoes are no fun at all (and very hard to use).

Which boat are you using? For 1984 use the Los Angeles. Fast, with plenty of tubes. For South China Seas use the Seawolf. It's OP once you get used to it.

Learn to hide. Stay the other side of the layer if there is one. Go silent immediately (SHIFT-S) once the mission starts, choose a depth (the deeper the better all things being equal) and a bearing, usually right-angles to the contact for better target acquisition from your towed array. Pay attention to the stats of the enemy. Do they have towed arrays? Learn to use the SCS COMP stats (google it), this is absolutely vital for success. Know that you need 200ft below you to use your towed array. This means that you can sometimes stay just above the layer with your towed array working beneath it.

Learn to evade. In a fast boat you can put incoming torpedoes behind you and knuckle. Don't use noisemakers too frequently - you only have a limited supply. SHIFT-T to crash dive. Do that and turn and torpedoes usually go over the top of you. Use a MOSS tactically - fire it before you get incoming to distract the enemy.

Use the strategic map to your advantage. Avoid shallow water where possible. If you're stationary on contact, you're running shallow and 5kn (best). Right-click into the contact and you're a bit lower and at 10kn (ok). Left-click into the contact and you're at 600ft moving fast (bad) - you stand a good chance of being picked up immediately.

If you can, maneuver round behind the enemy and watch the SCS COMP until you're in their baffles (behind them). In that position they'll never hear your launch transitions. For bonus points fire the fish away from them, turn your boat away and turn the torpedo in towards the target when it's a good distance from you. When the enemy notices, they'll retaliate in the wrong direction.

If you can't get behind them (as in convoy attacks), be prepared to pre-emptively fire a spread towards the enemy. Works well if you do it soon enough, as your torpedoes will be a good distance from you when they're noticed. You don't need a full solution to fire. An active torpedo tracking down the correct bearing works just as well.

Missiles are useless against anything with missile defence (M to check). They WILL give away your position. For land strikes, spend some time getting far, far away from the target first. Distance is no issue for TLAMs. If you need to fire 8 missiles and you've only got room for 4, fire them then get some distance immediately. You might as well cavitate at this point, the enemy knows exactly where you are. Consider firing a batch of 3 TLAMs and a MOSS. After a minute or two, go silent again, change your depth and direction, and move to another firing position. You can leave the mission immediately the last missiles have gone, no need to wait.

For SEAL team insertions, stay silent at all times at 50ft to keep track of enemy ships (remember you want 200ft below you). Don't attack anything except in an emergency. Airborne ASW will get you. Watch out for minefields, you can be real close as long as you don't actually touch one. Again, once the team is away you can leave the mission immediately.

If you can't do anything else, stay silent and slip away. You can't win every encounter.

A game needing to search in internet? This should be ingame.

Lol, it's not the developers fault you're a retard. Watch some videos of game play online if you need help. As far as Submarine Simulation goes, this is already on the arcade side of things. Whinging about it isn't going to get you anywhere.

Sadly I have to agree. Was a big fan of Microprose Red Storm Rising (and almost all of their other games) in the good old days and rather thrilled, when I found out there was a spiritual successor with modern grafics. But seriously - having to evade the same enemy torpedo for 15 times because it does not stop coming back at me? VERY unrealistic considering all that I know about submarine warfare, VERY unfun!
And all right: RSR is and always was arcady. But in a fun way. Even today, as I replayed it some years ago with DOSBOX. Throwing around your sub almost like a fighter jet evading torpedos left and right - or starting off with a pack of diesel subs all around you that start shooting immediatley, while still somehow saving the day really made you feel like the king of the seas. This does not! It's not a game, it's punishment... :(

Btw. I’ve spent some more time exploring this game - because I really would love to like and play this game.
Sadly doing this I also found some fundamental flaws in the game programming that really make me doubt the knowledge of the developers about submarine warfare.

Point one: detection
For example in a mission like "Iron Coffins", it is impossible to stay undetected even for a minute. Even if you go to 5 kts silent running, you are being fired upon within seconds. I now found a way to prevent this. Reliably. Even on Elite difficulty. You just have to stop the boat. Then you have all the time you need to get a proper solution and at least have a chance to fire first. Sounds great?
But that's b...lllsh...t from a real world perspective. The noisiest thing on a slow going nuclear sub is not the screw, it's the reactor cooling. So it should not matter at all whether you’re moving slowly or being stopped. Also if you stop the boat, the towed array sinks and looses it’s effect. So a real sub caption would probably never do this, but here it is encouraged strategy!

Point two: torpedo evasion
From the beginning this was the most frustration part for me – getting rid of torpedoes that detected you. In Cold Waters this is such a chore and always felt off, compared to other sub sims, especially Red Storm Rising. Knuckels are not really that effective and reliable, noisemakers are used up so fast – and those fu…ckers just don’t stop coming back. ☹
Best strategy seems to go to outside view and do some crazy last moment depth changes – which a real sub captain can’t do, because he can’t go outside and have a look, so he has a much less clear picture of where the incoming torpedo actually is. And which also basically is a game of luck.
So what’s wrong with those torpedoes in Cold Waters? Well, if you look at TTR when activation your own torpedoes it does not change a second, does it? That means an active torpedo can run just as long as an inactive one. What the heck, you ask?
That’s also b…llsh…it programming. An active torpedo usually goes much faster and thus should run out of fuel much sooner than an inactive one. Which would make evading torpedoes much less frustrating – if implemented correctly.

Point three: general AI tactics
Also there something seems off. I used “Irons Coffins” a lot for testing. As said above, if you don’t stop the boat, BOTH enemy subs start shooting at you within seconds. That’s not what a real world missile sub would/should do. It should stay silent, creep away and let it’s escort protect and defend it. Also once I kill the escort, usually the missile sub makes off at high speed and thus is a very easy target. Or I also had the boomer fight me and the escorting Alpha fleeing the scene… LOL
Complete nonsense. The real world purpose of a missile sub is to be a hole in the water. Ultra-silent, never to be detected – because they carry the nukes for nuclear retaliation if the homeland is attacked. Those boats are very valuable and have to be protected at all costs. And that’s not how the AI behaves here. Compare to a similar mission called “Boomer Bastion” in RSR: here the hardest part of the mission is actually finding the boomer. That’s how it should be and makes sense.

So conclusion: sadly I can’t really recommend this game. It looks nice, it has a lot of interesting features. The various campaigns could be a lot of fun to play. For someone new to sub games this may look like a great sim. Some even call it the best modern sub sim around! However the substance does not really seem to be there. The developers tried to make a carbon copy of Red Storm Rising, without really understanding a lot of (maybe a bit more subtle) things that were going on there. Fundamental things that 35 years old RSR got right – and this one simply does not! RSR might not have been the best or most precise sub sim around, but at least it was a good and balanced game and fun to play. Cold Waters is a worse sim than RSR ever was/is – and also a more frustrating and unfair experience to play.

What a pity, what a missed opportunity! With a bit more effort this could have been really good... ☹

I hope I am not beating a dead horse here - but maybe I was a little bit harsh on the game.
I stumbeled upon this thread over at STEAM where diffculty changes in game updates are discussed:

https://steamcommunity.com/app/541210/discussions/0/3277925755439250019/

Seems there are some issues with the "distance scale" option. Of course I set it to 1:1 for realistic - but it seems that's what causes some of the unbalanced and frustrating gameplay I encountered. Not totally obviously the game was designed and optimized for 1:2 and other settings don't work that great. Here - although torpedo range for the MK48 is still displayed as 35 KYD - running time drops from 26 to 13 min. So distances seem to be somehow shorter.
For me this also changed the the game from perversly masochistic to actually reasonably playable. It does not invalidate most of my criticism above, but as I don't have to play constanly on the edge, those effects are kind of glossed over and not that severe any more. If not every single torpedo comes precisely at you and you also have some margin to set up your own shots, overlong enemy torpedo running time is not that much of an annoying factor any more. ;)
Then again, the Devs were active in the STEAM thread and should have read about that issue. So why not fix it, why leave it in the game in the broken way it is. Also kind of lame and lazy. But with that setting the game is much more playable and feels a lot closer to good old RSR (which also felt like it was kind of sped up). And I guess that's what counts in the end.
So if you think you know about submarine warfare and still get totally creamed - frist thing you should do is check your "distance scale". :)