Fix: Retrieving birds in current is simply a matter of experience. Start by throwing a mark straight across a stream onto the opposite shore, and then send your dog. He'll drift with the current, and when he climbs the far bank, stop him with a whistle to make him sit and use hand signals to guide him to the mark. With repetition, he'll soon learn to fight the current, instead of drifting with it, to stay on a tighter line. When he's learned to hold a decent line to the opposite shore, start dropping birds into the current; first upriver of your position, so that the bird drifts to him as he swims, and then straight across, so he has to pick a line to catch up to the bird as it drifts away.