I don't know if this was in SHIII, I havn't played in awhile and even when I did the sea conditions made using the deckgun a hazardous adventure where just getting a hit was nice.....
Anyways I was reading in another unrelated topic a tip on targeting ships and I'm sure I am not the only one who was oblivious to this.
When targetting a ship with your deckgun, use AP ammo and aim for the water right alongside the target. You will know this technique is working when there is the splash of a water from the shell hitting short, followed by the explosion underwater of the round hitting.
The result? You are blowing holes below the waterline on the ship and it will quickly start tipping over.
Once the deck is awash start pumping HE rounds into the exposed deck and your target will quickly go down.
I am glad someone brought up the difference between when you should use HE rounds versus A rounds.. I always assumed AP was for warships.. but maybe I am wrong...
Also, in SHIII I used to deckgun a ship until it began to list.. then I would stop firing to save rounds and wait to see if she slips under..
In SHIV I've throwing rounds until I get the message "Unit Destroyed".. any reason in SHIV not to do the same.. pound until she lists and wait awhile..