One of Argentina's submarines apparently is missing. You can read about it here:
As a former submariner, my heart goes out to her officers and crew and their families. I think I know exactly what they are going through.
I also served on a "old" submarine (two of them in fact). The first was in danger of sinking on several occasions, and I personally helped keep it from going down more than once.
If they were having trouble in rough seas, they're screwed. Subs don't ride well on the surface in rough seas, and if they were taking on water and lost power it's very likely the ship has been lost.