Gonna retry the second mission of Dangerous Waters' campaign again. It's a really interesting mission. As the american side, after the start of a Russian rebellion, you are in a Seawolf sub and need to do some recon and ascertain the strength of their rebels in one of the ports they took, find if they have taken functioning SSBNs (Nuclear Ballistic subs, aka boomers) and identify who else comes to take a peek. Ideally without giving away your identity, it's all matter of managing how much information you let leak as you gather information yourself; there's all sorts of compromises. Periscope depth makes visual ID of surface ships easy, but exposes your periscope to visual detection, and forces you into shallow waters above the thermal layer where you're more easily detected. There's all sorts of trade-offs with raising any mast out of the water, as to what you're exposing. Even just passive listening can expose you, a towed sonar array needs you to be towing it to function properly, and your propellers are liable to be themselves detected by a good sonarman.