Convoy HG-76 Frederic John Walker and Walkers Exploits (A very good watch)
When a Uboat attacks a convoy all the escorts do the same thing at the same time to have maximum effect around the convoy on a planed line
as the war progressed and convoys had more escorts around the convoy walker invented the creeping attack with upto four escorts line abrest dropping dcs like a creeping artilery barage on the uboat then leaving two escorts in that area waiting for the uboat to surface to recharge batteries and replace the air in the Uboat .
The World at War (Wolfpacks)
with Convoy HG-76 and John Walkers tactics on attacking Uboats (25 minuets in)
https://www.dailymotion.com/video/x68qud0