Ducks do need to drink an awful lot of water. They use it to wash down food, to play in, to wash their faces, to preen with, to dabble in, to filter any goodies in it (mud!) and for the pure joy of making mess. They poop semi-liquid poops so need the water for this too. I would make sure that little ducky has access to water all the time in several places. I find that mine tend to forget where the water is sometimes and prefer to have several containers spread around, which also lengthens the time it gets mucky too. Perhaps as a youngster your ducky has not learned that it has to drink a lot yet? Might be due to being an only duck and not having other ducks to learn from? They do seem to do things as a group. If I am right about the only duck part?
Anyway, I wouldn't worry unless you notice raspy breathing or the chest going in and out quite drastically. Some beddings can be a bit dusty and lead to respiratory problems, but if yours is indoors this is probably not an issue.