[Armistead]

They cannot pick you up on the surface with sonar.

As far as submerge, mods do vary what settings they use for each sonar, however numerous other values come into play, mostly weather, but also running silent, under the thermal, etc. With active sonar, the profile of your sub has great impact.

As far as your crew, they will only call out sonar contacts within the range of type of sonar, but a game flaw is you can always hear contacts from the start of the war once they enter the zone. Simply, even if your crew doesn't respond or you don't, once a group enters in the zone, the limits of the best equipment available the entire war, the game spawns the group. If you pay attention you'll notice game lag when the game spawns a group in the zone, larger the group, the more the lag. You can take advantage of the by going to sonar and listening yourself as you aren't limited.

Only danger you'll have on the surface is radar, which you'll notice when a escort comes at you fast. Some later escorts and DD's have radar later war, so you'll see some in some convoys. Obvious, attacking on the service in a storm with fog, you can't see. I usually with the APR see what ship has radar if any and start at the end of the convoy he isn't on. Almost ways they try to run up behind you. If a large group, I'll get to about 600 yards and shoot the deckgun or 40's by bearing out of site. Usually u start a fire or a light blinker comes on making it a easy target in the fog. Be careful getting too close, you sink a ship loaded with fuel or ammo, the blast range can reach out and damage you or even blow you up. If a radar ship gets within 2000 yards I'll got to radar depth, usually they go back to their station, then pop up and go back at it again, sometimes dodging in and out between ships using them to block. It's rather easy to take out a complete convoy on the surface in a storm.