Argentine navy loses contact with submarine

This was probably a horrifying way to die. Most submarines won't go deeper than 200m on operations, maybe 300-400m on a deep dive test. The deep dive test depth is 50-70% of the theoretical max depth. The max depth isn't tested physically, of course.

If the Submarine lost control/power due to system failure, the crew could have been watching them selves gradually sink on the various depth guages around the boat. Once they went past 300m, they would have known that it was only matter of time until they reached crush depth, when the sea pressure would crush the submarine and everything inside it. Essentially, you would be watching your life tick away on a plummeting depth gauge.