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.