I upgraded from 18.4 to 18.12. Waterfill now seems to be broken. When selecting waterfill, the placement icon looks like the new offshore pump icon and waterfill will not place.

what other mods are you using? maybe its a conflict between mods somewhere.
i just checked and it is working ok for me in 18.12, would it be possible to send me a copy of your save game to have a look?

I got the same issue ! on factorio 0.18.19 with the followings mods
- all the factorio extended mods
- LTN
- even distribution
- fill4me
- Atomic artillery
- laser tanks
and some other cosmetic or QOL mods
hope this can be usefull !

EDIT : it was a weird behavior with the mod canalbuilder
works great by itself on 0.18.21