The Manual is sadly lacking in detail on any of the missions you might encounter, but especially so for the Special Operations. For a rescue to be performed, you have to have a "Survivor", which would be simulate downed pilot. If there is a pilot capable of being rescued, you would see a pink glow, more easily seen at night, but able to be seen during daylight also. This is also sometimes a "sonar line" emanating from them. You have to drive your submarine to within 400-700 yards of them at a minimum, depending upon conditions. Just like with gun targeting, it is easier to get them just off the port or starboard bow than it is from the side, due to the pitch of your boat, but also from possibly being in too close and unable to "target" them. Targeting them requires you to be on the Bridge view, using your binoculars. Similar to "targeting" a ship for gunnery with the spacebar, you would press that Rescue button when you have the pilot survivor in view within your binoculars, and the crosshair goes from yellow to red - press the button and if all goes well, the pilot is magically on your boat and being attended to by medical personnel, and asking about lunch. There are missions with Rescue as the objective, and you might have to pick-up five "survivors, you might have to pick-up ten. Seems to me that the earliest you'll get one is later 1943, and some do attempt to coincide with actual real life missions, but most do not. They can be stressful, because you are on the surface (and you'd better be at battle stations, guns manned), and the shtinking survivors drift and move away from you... You almost have to "track" them sometimes.
So Life Guard duty, you have to be on the surface, manning the bridge using the binoculars. Insert missions with supplies or agents, you have to surface and get the prompt to launch. In both cases, very low speed is required, and you have to be within a designated area. Photo missions also have a defined area, you have to use the periscope, you have to "Lock" the target, you have to use the Camera button, and you have to be close enough and targeting the correct target...
