Yes! But this means that "the cats don't like water", in other words, water is a kind of thing that they don't like (for example: "as gatas não gostam de água quente" = hot water is a kind of thing they don't like).
"As gatas não gostam da água" can mean this, but can also mean that they don't like a specific water (for example, when you put warm water in their water bowl and they don't want to drink it: "as gatas não gostaram da água" - only notice that this last sentence is in past tense). (I'm not a native English speaker, so don't hesitate to correct any error in my text if there's one)
I would bet you are far beyond the need for this answer but a lot of others are still questioning so I will answer you for their benefit. :)
Gostar as a verb requires, "de" as a preposition kind of like English "wait" needs "for" or needs to be changed to "await" instead. So now we know that the sentence must include "gostam de" (plural 3rd Person conjugation to agree with "cats/gatas").
But since we are being particular about what water (perhaps tap water with high chlorine, or water we have put their vitamins in), then we add, "a" in Portuguese to agree with the feminine "the" of áqua. That makes the sentence, "As gatas não gostam de a água." which is awkward with all those vowels including two the same bumping around against each other.
That is perhaps one reason that Portuguese requires contractions (and is exactly what this exercise lesson is trying to teach) for de + a to make, "da" as a combo word.
That is the feminine (to agree with "água" not "gata").
The masculine is "do" (de + o).
In other exercises we learn that "pensar" (to think) also requires a preposition which is "em" (usually translated to "in/on") which contracts with "the" to form, "na and "no" (which usually means, "in the" or "on the" but sometimes means, "of the" or "from the" (and "at the" on occasion) since "de" preposition does not go with "pensar").
Hope that was clear. :)
Scutigera gave an excellent answer to cazort's question above: https://www.duolingo.com/comment/506965$comment_id=13782047
It happens occasionally, but not too often for any one users. I think it has to do with distortion or corruption of data over the internet. But be aware of it. It might also give you some other accepted answer, making you think some detail of your answer was wrong when it wasn't. But it may not happen to you again for a while.