[UKönig]

If you are part of an HK unit that has located an underwater U-boat, then you are about to embark on a rewarding experience that will likely end in a kill.
The lead escort ahead covers the forward arc, the sweepers along the side protect the flanks and the one "walking drag" will often mop up.
Later in the war (but not too much later) Hunter-killer groups will tag along some distance behind, but ready to accelerate to 35 knots when the sweeper or drag units have confirmed a U-boat in the area. The HK units will then take over the task of destroying you and your boat so the escorts can continue with the convoy. The hunter killer units have no other job than to make sure that you are dead. No softer fate awaits any boat forced back to the surface either. It's not too easy to surrender. The Tommies want to see red, for there at last is the enemy in front of them, for whom they've been staring themselves blind. Days, weeks, maybe months on end with no peace or calming nerves, the tormentor torturing them, even when he was a hundred miles away. Nobody in convoy can ever be sure that he's not being watched from the trough of some wave by that cyclopean eye. And there she is suddenly, the viper that drew blood. Nobody can blame them really....
If they are good, the enemy captains will take turns. The U-boat will never really know which of the escort units is attacking it. The first captain will hold the boat in ASDIC and radio that information to the attacking ship, which is going too fast to use it's own sets properly. ASDIC is useless at high speed and normal hydrophones are deafened by the water streaming over them. ASDIC detection is not dependent on sound but magnetic anomaly, or, the mass of the U-boat in water. Or part of it is, I'm no expert but the sonic ping and return cannot be concealed by stealth. It's been described by those in the know as stones thrown at the hull. Being quiet will only help you lose contact if you are able to get below the jet stream. The salinity of ocean water hinges on a few things and even stuff like too much plankton can disturb it. The short version is, by diving below thermal/salt layers and going to quiet mode a submarine can make the HE operator lose contact. This is when the HKs will go back to their usual tactic, carpet bombing at random. Maybe if they score a hit, do some damage or make the U-boat make more noise, vis-a-vis damage control, they can start being more accurate again. And an oil slick is unmistakable evidence of a direct hit. Once the blood of the boat has been drawn, the next rule is "Don't stop until the Captain's cap floats up".
This isn't always represented in a game but like I said, I learn the reality and the history behind it and carry on as if. If not, then I don't worry about it, it's just a good habit to get into.