My ducks were kept in a coop until their oil glands developed. I wouldn't even let them out of the coop to forage. We have Hawks and owls all over the place . So when it came time for them to be introduced to the pond they didn't want anything to do with it. That is until they saw another duck in the water. Could you put cracked corn or some other treat in the shallow water and some leading into the water. Get them foraging in the waters edge and they'll go in.