Posted this a while back on the DF subreddit, but thought I'd share it here too.
So I noticed something interesting today as I accidentally flooded my fortress in an artificial lake I built. Long story short, floor collapsed during building and punched a hole into a section under the artificial lake, lake empties, fortress becomes an aquarium.
Anyways, down below in the sleeping quarters I noticed that a few dwarves were trapped in their rooms. I decided to observe them out of macabre intrest to see if they did anything interesting.
Apparently, when dwarves get hungry and thirsty enough they will try to brave the waters. One by one the dwarves tried their luck in getting out of their individual bedrooms, but the pressurized water was too much for anyone and nobody made it further than a couple of tiles. Interestingly there is quite a lot of variation in the time it took for each dwarf to try it, some of it probably comes from when they last ate and drank, but few of them took a lot longer to build up the courage to try to leave. A couple went within a week, most in a couple of months and a few waited until practically dead from thirst already. Hunters and military members seemed to be the first ones to try. Some also tried to hunt small animals in their rooms, but not all. Few opened the door and managed to close it before the room flooded completely, they waited quite a long time until trying again. Children waited until the last possible moments to try to escape and one at least tried to hunt small animals in their rooms prior. That one was abnormal from others who played makebelieve by themselves until finally trying to leave, still playing as they drown, or starving in their room.
My mayor survived quite long and was one of the last stragglers and resisted opening his front door. He eventually did though but managed to close it before his first room flooded completely and then retreated to his bedroom. After that he started frantically running around his bedroom in a panic trying to hunt small creatures, he did not do this prior to first opening the front door. Curiously his thoughts didn't change after starting to panic leading me to believe there is more going on under the hood. Finally, after a while longer he tried to escape again and drowned in his front room.