Need some tips on team building

I’m playing a casual playthrough at amphitrite city and was wondering what the final member of my team should be.
I currently have:
Zebstriker
D. Venasaur,
D. Snorlax,
D. Chandelure,
Flygon

I like the look of delta goodra (not too worried about the ground type double up) but you get it so late game that I was worried it would be a waste of time. Are there any potential substitutes for a strong water type, or should I just wait and see what happens?