How do they detect you when on the bottom?

[Poacher886]

I just had an end to my first campaign...its was short 10/09/39. After damaging a couple of troop carriers in a medium sized convoy off east England, i noticed an Escort heading my way, so i dived.

Not realising the relative shallow depth of 70m i soon hit the bottom...going to external view to check what the noise was about (im still new to SH5), i found my boat 'Actually' on the bottom (as in not floating 20m above it!) and to the side of a big boulder.

I decided to sit it out with all engines off and crew at silent running to see the result, sure enough the ASDIC pings picked me up and before i knew it, i was to damaged to move....despite letting of decoys, i was a sitting duck and the single relentless destroyer made many passes before finishing me off!!

My question is though, how do they detect you??, if im not moving, then they cant hear me, im not on the surface so they cant use radar, and surely Asdic will detect an object moving in the middle of a body of water, but if im motionless on the bottom, i would have thought it would just bounce of the bottom of the sea bed like it would off any rock or formation under the sea.

How can they tell that its a U-boat on the sea bed???

[Scoochy]

Sound bounces off metal differently than the sandy bottom?

I believe it has to do with how they hard coded the game. They didnt incorporate hiding on the bottom into it. At least thats how it is for us folks with SH3 Im not sure about 4 and 5 but Im pretty sure itd be the same thing.

If not my guess is he picked you up before hand on hydrophone (if you were making noise) or got lucky and guessed where your torps came from and just started making runs when he hadnt picked you up

[BogdaNz]

it's does matters if you are moving or not moving,the ASDIC will detect you.the sound wave struck a submerged object like submarine and it is reflected back and picked up by the receiver .
you say how they detect me if i am not moving ,the answear is up.

[Sailor Steve]

Not necessarily. There are several incidents of submarines successfully hiding on the bottom in shallow water. The bottom absorbs the sound waves, or reflects them in odd directions. Also the sand absorbs the shock waves from the depth charges, enabling the sub to survive several hours of attacks. On the other hand, while we know about the few times this worked, we don't know exactly how many times it failed.

Unfortunately the game models none of this.

[BogdaNz]

Originally Posted by Sailor Steve

Not necessarily. There are several incidents of submarines successfully hiding on the bottom in shallow water. The bottom absorbs the sound waves, or reflects them in odd directions. Also the sand absorbs the shock waves from the depth charges, enabling the sub to survive several hours of attacks. On the other hand, while we know about the few times this worked, we don't know exactly how many times it failed.

Unfortunately the game models none of this.

you talk here the u-boat attack in 1942-1943 which terorized the Saint Lawrence River(canada).There the u-boat was practically invisible,because was hidding by turbulance water of river,and remains undetected.The destroyers never get a solid contact of u-boat ,u-boat was invisible .

[Hottentot]

In shallow waters and clear conditions I think it is possible in real life to occasionally simply see the submarine, especially from the air. Not sure if that would be the case in the Atlantic and 70m sounds pretty deep for this, though. And even if it was possible, I don't believe it's modelled.

Edit: I was thinking something along these lines. Those are in periscope depth, but you get the point.

[Sbygneus]

I agree with Bogdanz. Its ASDIC that detects you. The seafloor is mostly flat, apart from rocky shore areas, reefs or deep ocean mountains which are not the case here. For ASDIC, a laying submarine is a clear obstacle of high density material (low wave absorbtion, high deflection). However, there seem to be a chance to lay in some kind of seaflor ditch or trench and thus make ASDIC detection very hard. In a book about Operation Paukenschlag I read about Hardegen's U-123 succesfully hidden this way once at the East coast of US.

[MoN]

Originally Posted by Hottentot

In shallow waters and clear conditions I think it is possible in real life to occasionally simply see the submarine, especially from the air. Not sure if that would be the case in the Atlantic and 70m sounds pretty deep for this, though. And even if it was possible, I don't believe it's modelled.

Edit: I was thinking something along these lines. Those are in periscope depth, but you get the point.

There is no way to see the ground 70 meters down as water absorbs all light within 60 meters even under perfect conditions. Being on a plane obviously does not help.

I've seen the wreck of a ww2 corvette at about 35meters in the red sea from just UNDER the surface and you could barely see it even when knowing exactly were it was.

As the red sea is way clearer then the Atlantic/north sea and there was no distortion from the surface I'd say it's impossible to see a u-boat below 30m or so.

[Sailor Steve]

Originally Posted by BogdaNz

you talk here the u-boat attack in 1942-1943 which terorized the Saint Lawrence River(canada).There the u-boat was practically invisible,because was hidding by turbulance water of river,and remains undetected.The destroyers never get a solid contact of u-boat ,u-boat was invisible .

No, I wasn't talking about that at all. I was mainly referring to the adventures of S-38, which attacked the Japanese fleet in the Lingayen Gulf in 1941. She grounded four separate times and survived over 36 hours of on-again-off-again depth-charging.
http://en.wikipedia.org/wiki/USS_S-38_(SS-143)

[Catfish]

Hello,
Hardegen also reports being overrun by destroyers numerous times at a depth of some 30 meters, also Topp, also Prien, and some others.

"How do they detect you when on the bottom?"

They don't. In reality

Greetings,
Catfish