At least in the submersible, you can practice being calm as your life is being taken. You still have a bit of freedom to move about. It’s still terrible.
There is only one worse way to die and that’s in a cave from spelunking and you get stuck so you can’t move at all. That terrifies me out of my mind.
https://www.dailystar.co.uk/news/weird-news/the-worst-death-imaginable-spelunker-22880796
I very much agree with you. Trapped without air is the stuff of nightmares.