האיש הרע נפל לתוך המים וטבע
should be acceptable
Yes. Also, I would never say נפל במים in the sense of "fell into the water", I would say נפל למים. But possibly this is a matter of different linguistic communities, maybe someone else would comment on that.
I put the same thing and was rejected.
נפל במים is wrong
so I have reported it. They also need to accept איש.