I have a small pond and 2 Muscovy ducks (girls). Yes, it happens that they won't come in, but it is my fault. They do not see well in the dark or semi-dark, so you need to bring them in before sunset. If they can't see they sit still in the middle of the pond. For the times there is an issue, a long handled broom is the answer. My husband wields the broom and makes them come to me, and I scoop them out of the water. (then my spouse and I bicker about whose turn it was to bring them in early enough that we don't have to do this

) I have also shone a bright light on myself so that they see me and swim towards me. I have never given up, but it is a small pond and we have lots of wild animals up here ... also, I am a worrier, so no chance I could sleep while they are outside. (and if I don't sleep, neither does my hubby!) I have another trick... when I give them mealworms I shake the glass jar I keep them in, so the sound of the mealworms shaking is a mighty strong lure!