Another tactic I use often is to surface close to a damaged merchant, and set a torpedo to fast/magnetic 000 heading and put a shot into the DD amidships as it crosses the freighter's bow.
I have also surfaced next to a merchant in a convoy, below their cone of fire, and allow the ensuing destroyer fire to badly damage and/or sink the vessel.
I can then hide under the stopped hulk and pop up scope periodically and broadside the DD's.
|