They just freeze over at some point...I try to break the water up as much as possible, but when it's subfreezing for extended periods of time, as with this winter, it's impossible to stay ahead of it...However, overall, they were accessible more than they weren't and when they aren't, they always have FRESH water buckets we fill every morning and night for them...
The hose doesn't even work here in the winter though. Sounds like I'd have to have a barn with running water to keep ducks happy through the winter. My coop is about 20 yards away from the house. Not sure how I could get that much water out to them even if it was going to freeze by the end of the day.
Or would they be happy enough with buckets?