I saw one that had a funnel type interior with arched top holes in the wall of the bucket to allow the ducks to get their heads inside to grab food.
The base looks wider than the bucket which would allow rain/snow to build up and make a mess of the feed. You can build a flat roofed station to hang it under (or another feeder) to help protect the food.
When I have watched my ducks eat they seem to scoop the food up a bit. If the base was wide enough to scoop it would probably work but unless it's under a shelter it's not going to keep the food dry.