Very sad but also very suspicious. There is a billionare on board of this submarine. Titanic ghosts? Pirates of the sea? Let's talk conspiracy...
Seems like a fitting topic for this community. My guess is that the rebreather system failed and the crew/tourists passed out and died before they even knew something went wrong. However, sabotage is always a possibility...
I think, given that debris has now been found, that the reports of hearing tapping in 30 minute intervals was either totally made up or cultivated by the news media to further capitalize on a news sensation and keep us looking for updates on their potential rescue. That's a conspiracy I guess, right?
I'm not saddened by this. Its like hikers dying on Everest. Probably shouldn't be there in the first place and if you die doing it, well.. that was kind-of the point.