Question regarding a specific side mission

[PanicEnsues]

For rescue missions, you just have to maneuver your sub so it's surfaced and inside the green ring that you should see in both the chart view and from the bridge.

Once you enter that ring, a timer will start; remain inside the ring (and surfaced) until the timer runs out, indicating that the rescue op is complete.

If you leave the ring or submerge, the timer will reset and you can try again.

Hope that helps!