After the first week ducklings do better without a chick waterer. They just can't help themselves and will make a very messy brooder otherwise. Most of us switch to a plastic container filled with water and holes cut in the top (or side) which are only big enough for their heads.
Personally, I give mine swimming water early. We start with a pie pan when they are two days old and move up a little each day. By a week old, they have swimming water all day (I keep an eye on them). I do lock them in at night. Funny thing is, the brooder stays drier this way. The water stimulates their oil glands so they also get water proof fast. A mother duck would have them on a pond at an early age. Here is a video of some of my past ducklings playing.