You would think that even a brain-damaged lemur could figure out that it would be a bad idea to idle in a room filling up rapidly with water. You would think that a supposedly "intelligent" life-form would have enough sense to get the hell out of there as soon as they were done building the water wheel that was designed to flood the damned room. But nope. On five different savescum loads to try to spare unlucky Dorfs from drowning due to their own stupidity, I've had the same scenario occur. Allow me to expound on it.
Urist McCarpenter: There, water wheel's done. I'm gonna stand back and admire my work.
Rapidly-Flowing Current: *whoosh*
Urist McCarpenter: Aye, it's working well. Huh. This room's getting mighty wet. Maybe I should try to get out now that I'm in water up to my chest.
Backwashing Current: *floosh*
Urist McCarpenter: Ach, I've been sucked out into the channel! Well that's no good. I've no choice, I'll just have to drown, even though I could easily get out with the huge set of ramps set in place to prevent this kind of thing! So long, cruel world!
Urist McCarpenter has drowned.
Olin McMason: Somehow I know my buddy Urist drowned, even though I'm half a mile away making a floodgate! I think I need to throw a tantrum now!
Rest of Fortress: We'll help! *epic tantrum spiral*
Your settlement has crumbled to its end.