We trained our dog to “get the duck”. Mac just loves barking at them to scare them away.
(He also protects us from airplanes and thunder.

)
Another safe option is a long-range super soaker squirt gun. They really don’t care for that and the kids just love it.
(Then you will have the problem of everyone getting soaked.!

)
Usually the ducks do stay in the lake, but last year a very persistent female duck kept coming around to the house deck for handouts. (I strongly suspect someone in the neighborhood had been feeding it.

) I was afraid to let Mac go at her on land – what if he caught her?

Since my first two options didn’t work, (The squirt gun was always in the wrong place.) I scooped her up, brought her down to the dock. Set her at the end and held on to her. Then I had my son get Mac and put him on the shore side of the dock. One, two, three – let the dog go! The duck never came back.

Good doggie.
You know what they say, no harm, no fowl.