"L'eau est bonne."
Somewhere during the introduction to adjectives, the student needs to be given an understanding that the form of the adjective is dependent on the gender of the word it describes. I had to go research this on another website to get a better understanding -> http://www.jump-gate.com/languages/french/french4.html
Go to Google translate to translate words and phrases less reliably but with the option of sounding out the words for you. Very helpful for use with Duolingo's robotic pronunciation issues.