Why a person who doesn't believe in God or an afterlife would find everyone drowning so troubling.
Drowning takes only a minute or two at most. After the first gulp or two it should be relatively painless (a lark when compared to a knife in the gut or a Saturday night special through the wherever, the Big C or the wife catching you in bed with her sister and mother).
And when it is over, it is over. As I understand not believing - If you're dead, you can't be all that disappointed in missing the neighbor's BBQ, can you? Or do you know something the rest of us don't. Please don't tell me that non-believers worry about what happens after they die if that death also includes everyone else.
For the non-believer, it seems that everyone dieing would be a "boring so what".
Death to the entire race could be a big problem solving solution, too. If a non-believer were even mildly concerned with global warming, they might consider that total elimination of the human race would be a pretty good thing for mother earth. In fact, mother earth would do just fine without any of us here.
Just a few random thoughts.
Anyhow, I thought the latest Ark movie was supposed to be a farce, sort of like Ace Ventura in a big row boat, with a beard. For a factual look at disasters of planetary scope, you might want to consider Discovery channel or National Geographic, or National Enquirer network ad let Hollywood do their thing in their way. This film struck me as a pretty good date flick for 13 year olds. Looking at it in that light, it all makes pretty good sense and should make someone boo-coo bucks.