Oh. Try reporting it.
Haha! Took me a moment to get it, but that was pretty good.
"The water level is very high" is a valid translation.
I thought this was the procedure. I'm not sure how to report it from here at this point until I see the sentence again.
The procedure is always to report in loco when you see the sentence - if you're unsure, send a report anyway (the creators will get our reports in bulk when they log into their special software, but you need to report them the right way).
La akva nivelo estas tre alta?
I put, "The water-level is very high", and Duo told me that I was nearly correct. They gave the "correct" answer as: "The water_level is very high". I have reported it.