I've had one three months or so and it is a good training tool. Watching my dog go submarine six or eight times was worth the cost of the dummy.
I have noticed that it will pep up a dog that is not an enthusiastic retriever. The dogs like playing its game. I would like for it to dive better than it does. It seems to work even better when you are training from a boat.
I finally got this Diving Dummy out this weekend. It really adds some pep to the end of a retrieve after using it one 3 or 4 marks. It only seemed to dive about 6 inches. It was enough for Ginger to stop to see where the dummy went to.
In my opinion, it would be good to use on a pup before their first hunting season. After that, it is a fun gadget to use with the pup once and a while to break things up.
Had a diver since last year....wouldn't dive very far until I made some modifications. To get it to dive deeper, easier, simply attach a 3/4 - 1 oz. lead slip sinker to end of the cable that attaches to the fishing line. Mine now works fantastic, but you have to be more careful when casting....it's easier to have it break free prematurely.
I got one about 3 weeks ago. Finding divers has always been my dog's weak spot. After 4 training sessions with it, I can see a real difference. As others have noted, for some reason it is really exciting to the dog, so the training is fun. I also felt that it did not dive quite as deep as I had hoped. I think the sinker suggestion is a great one!