GZDoom underwater air.

[Barry]

I want to ask if there is a way to see how long you can stay underwater, like for example a airmeter that shows how long before you run
out of air and start to lose health. The thing about it is just when you have low health and you are underwater, you want to know how long
you have before losing health and die, so that you can try and swim as fast as possible to safety.

[Gez]

See this thread. It'll tell you both what exists and what doesn't exist yet, as far as this question is concerned.