Usually, you don't, but, if you were throwing a water mark that fell behind a log, for example, and the dog made it to the up wind side of the log and couldn't see or smell the bird, it would be permissible to handle. In the case of a drifting bird on a windy day, if a dog makes it to the original fall area and the bird has drifted away, it is permissible to handle to the bird. Perhaps you're testing in a body of water covered in thick duck weed. Often the bird will "disappear" after it hits. If the dog gets to where the splash was, the handler can handle with no penalty. These are just 3 examples. Hope they help.