Although I have not seen all the nominated films I think the winners would be the following:
For this category I´m going togo with Shape of water, this movie have so many amazing scenes where you can see all the imagination that Guillermo del Toro have that is just so impressive.
"Dukirk", In my opinion I dont like this movies, but the backgrounds that this movie have can´t be compare.
In this category I will said "Guardians of the Galaxy, Vol. 2" the visual efefcts of this movies is very awesome, the character and the scenes they look so real.