Welcome aboard!
I don't have any experience with hydrophone attacks, so
I can't help you there and one of the GWX gurus can probably answer your Steam/GWX question.
As far as night attacks go, alot depends on when in the war you are attacking. Late war(late '42 and on) escorts come equipped with radar and get better at using it as time progresses which makes any type of surface attack difficult to say the least.
Early war attacks can be rewarding. The key is patience, slow speed, and run with decks awash. With those keys, positioning yourself ahead of the convoy before you make your attack is very important. Running around at high speed is a sure way to be spotted.
Weather helps. Clear and calm conditions make it difficult. Some wind, light fog, and lowered visibility make things easier.
I don't think there is anything more rewarding in this game than making a night surface attack, watching the escorts search in vain for you while you slip away on the surface, and repositioning yourself for another attack. I've done it a few times and it is a good feeling.
Those chances dissappear as the war progresses though.
