Seth, congratulations on your successful outing and new retrieve companion.
I've taught two labs to dive after crippled birds. Basically, just start working with a dummy held in your hand in shallow water to get the dog to put their head under water routinely to make the retrieve. As water initially flows into their ear canal the first couple of times, the dog may pull-back, just stay at it until it becomes comfortable with immersion. I eventually shift over to a weighted dummy that sinks slowly, and work the dog in shallow clear water. After each workout, make sure their ears are cleaned and dried, particularly if the water is standing and slightly stagnant-big advantage of doing this type of training in Lake Superior!
I taught my chessie to dive for bumpers in really clear water also. I just tied the brightest chrome end wrench I could find to the bumper. Both the bumber and wrench showed up against the sandy bottom. It worked really well. I'd just drop it off the end of the dock in front of her and away she went. I'm not sure I want to get that intense with my wire-hair yet he-he she only weighs 45 lbs. I'm still amazed she caught those cripples. She just doesn't look as fast of a swimmer, as the chessie was. But all things considered she's really not designed to be the perfect water dog, like labs or chessies. She's a long range, big running, upland dog. Heck, I had even taught my chessie to retrieve people. Can't see Rhyka being able to do that. What I have taught my GWP to do my chessie didn't was... blood track big game, shed hunt antlers in the spring, and tree racoons. Besides her bread and butter upland pointing. So she's much more versatile but everything is "does it pretty good" not perfect, but fair enough for me. A dedicated water dog you can really focus on just one thing... retrieves. My annual Veterans Day (Dad lets me off the ranch, since I am one) hunt is coming up. So if the stars line up I'll carefully, under the perfect circumstance, making sure it's dead, and not sending her if it isn't...see if she can handle retrieving a goose in the water. I couldn't get the geese to commit yesterday, but I only had two honker dekes out. On a side note many moons ago my cutter hoved two in the ice over the Edmund Fitzgerald. Pretty moving....-Seth Freeman