A couple-three pointers: You can see the "pink" from afar off, your crew cannot. You cannot rescue until your crew says they have spotted the "Survivor", which I ~think~ they call out "Ship spotted! bearing..." This will generally be 400-600 yards from the "Survivor". Some missions, they "drift", some missions they drift a LOT. Try to figure which direction they are drifting as you approach, and then approach from the side they drift to. I usually use Ahead Flank to close on distant "pink clouds", Ahead Standard" on ones closer, but Ahead 1/3 when getting closer. As you hear the "Ship Spotted, if you are on a seemingly good course to catch them, go to All Stop. You have to be on the bridge, with the bridge menu below, use the binoculars and anticipate your aim for the cross-hair to turn red as you put your mouse on that life-ring menu item and click. Generally speaking, the closer to 0° you are to the pilot, the less pitch you will have. As you get toward 90° or 270°, you will experience the most. Somewhere between 345° and 15° works best, but don't let sub parts like the bow sprit get in your way, and do not run over the "Survivor"... lol - They do usually survive, but it will take them a time to come back up, and it's usually not very close to where you are...

- Rough seas are the worst, as you found out, but you did it! Practice makes perfect! Toward the end of 1944 onwards, that was one of the main, most important chores US subs did. Here is a pdf we found several months back while doing some research for FotRSU mod, but haven't implemented yet: "
Mission: Lifeguard". Good stuff. Adm Chaz Lockwood wrote a book
Zoomies, Subs, and Zeros (SubSim link), on the subject, written in the Lockwood style of his other books.