Another Sub Sinks to the Sea Bed

I’m not sure how got mentally involved when I hear about a submarine accident. One of the earlier incident was when an Indian sub went down with all it’s crew. One of the worrying thing about submarine accident is the high fatality rate. In most incidents, all the crew looses their life.

This is something very worrying about the life of sailors in submarine. And that makes a common man think, what’s the way out when a sub sinks to the depth, either due to power failure or any technical snag.

Is there a way to hold the sub at a level at least for sometime, till it gets help?
Is there a way to release some kind of air filled balls to make it float.
Or just like life boats, is there any way to have an escape cute from the submarine?

Or another simple way safety mechanism by which subs can release air filled buoys to help rescue team to locate the position of the sub.
Also, is there a black box, just as in a plane to know the last moments of the crew.

One thing is for sure, that most subs currently in service don’t have to be in active combat. Mostly they just do surveillance and routine runs protecting the territorial water. So, in that case, a part of the sub should be dedicated for safety purpose.