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Actually, the formation was a line of waiting U-boats called a 'rake formation' generally ahead of an oncoming convoy stretched miles across the convoy's presumed general path: zig-zag tactics included, usually shadowed by a reporting scout boat with orders not to attack until the 'rake' engaged. The tactic had mixed results possibly because every U-boat commander would engage on it's own initiative as the Germans, commanded distantly by Doenitz, never felt the need for an 'onsite' field commodore to coordinate such a wolfpack attack on a a hapless convoy. https://uboat.net/ops/wolfpacks/overview.htm