OK. I know the tactic - just never heard it called Swamps before.

Normally allied escortvessels could not afford to stay on top of a \'cornered\' submerged U-boat and hunt/pound it into submission because they couldn\'t leave the convoy undefended. If a kill was not achieved after a few hours the vessels would have have to be satisfied with holding the boat under long enough that it was \'left behind\' of the convoy.

After allied ASW got to a very high level in quantity, they could afford to leave ASW vessels on top of a \'cornered\' U-boat and pound it till it either was sunk or had to come up for air - days if necessary. Special hunter-killer tasks forces were also made to dash to the site of a cornered U-boat and hunt it till exhaustion. Very effective, if you had the assets. Don;t think it came from wolf pack tactics per se. Just the increasing level of assets allowing the ASW commanders to do what they always wanted to do but usually didn\'t have the luxury of doing: hunting a boat to exhaustion.

The crews knew the odds by the comrades who never came back. By 1944 everyone knew a U-boat patrol was almost suicidal.