With all the recent, and continuing, rain events around the NSW east coast, the ability to report water over the road would be very helpful. We are all directed not to drive through floodwaters but where there is some standing-water covering even a short section of road, it can lead to aquaplaning or hide potholes, so I believe would be a useful addition if listed separately as a hazard, like potholes etc.
Hi world_w3hfih41,
You sure can, I often get these reports on the way to work! 
Click on Report > Hazard > Weather and you can use the Flood option. This lets drivers know there is water over the road as you’ve recommended.
Waze makes an important distinction however between “flooded” and “road closed”. If the road is completely closed, you can also report the road closed if you’re using the Waze app on a mobile device. This option might not be available for in-car systems yet, but I hear it is in the works. On the Waze Mobile App, click Report > Closure and tap the applicable arrow. Note these closures are one way only. And please make sure you stop your vehicle safely before taking time to apply the closure.
Take care! 
Many thanks, Brendan. Much appreciated.