[sublynx]

Here's a hint on those people who have type II's and want to add one more ship to their ships sunk list: the merchants have a lot of cargo on their decks. If you hit those cargo crates a couple of times with that pesky 20 mm gun of yours the crate will magically explode, causing major damage to the ship. If you explode all the crates, and also the life boats (for some reason they explode too, when hit), you might well be able to sink a small 1800 GRT small merchant or steamer just with AA. This is also a good thing to remember when finishing a bigger ship previously damaged by a torpedo. First pick the crates and lifeboats with AA, then pound the waterline with the deck gun.

It's not very realistic maybe, but on the other hand U-boat Commanders Handbook orders that you first suppress the crew at the deck of the target and only after that hit the ship where it hurts.