"The water flows from the shower" is more familiar and should be accepted.
The water 'falls' is the same as 'comes out' in this case. Both are correct. No reason for marking it wrong
What does it mean? The water falls from shower head down to the bottom of the shower? The water is turned on in the shower? The water is falling out of the shower tray (and on to the floor)? I'm not trying to be difficult, I just want to understand. Thanks
Unlike Paulo, I have to consult a dictionary to learn all the meanings of a Portuguese word. Having done that I'm led to believe that in the right context "chuveiro" can mean a shower of rain if that includes flurries of very strong rainfall or a sudden and fleeting downpour, however, virtually every use of the word "chuveiro" I've found using Google has been a reference to a bathroom shower or showerhead.
(Speaking for Brazil) I would never ever use "chuveiro" for rain.
A strong rain could be called "chuvarada".
I'm constantly amazed by the disconnect between usage described by Brazilian dictionaries (such as the two I've quoted above) and reality. If you look closely at the Michaelis entry you'll see that the primary definition is "pancada de chuva muito forte".
There is still the possibility that "chuveiro" is used in Amazonas because the dictionary says it can mean "chuva de inverno" there. My confidence that is a fact is not too high. :)
In English we just wouldn't say "falls from the shower" - we might say "falls from the showerhead", because for us, the shower is the whole little cubicle, while the thing mounted on the wall is the showerhead, but more likely we'd say "falls in the shower", because it's the place the water is falling.