While it is true that retrievers like to swim, they will naturally see the water as an obstacle and attempt to run along the shore rather than go straight through the water to pick up a bird. Shore breaking your retriever is not difficult if you have some dummy bumpers and an electronic collar on your dog. Electronic dog collars are waterproof and give your dog an unpleasant sensation, but do not hurt them. Electronic collars are the best way to shore break your retriever.
Use the bumper and toss it into the middle of the water. Your dog will want to go around the shore instead of jump right in. You will then need to change his path. Using the electronic collar, you can then give him an electronic impulse. Lead him into the water to get the bumper. He will soon learn that this is the best way for him to get the bumper, rather than go around the shore, a path that causes him discomfort.
In addition to wanting your dog to go into the water to retrieve ducks and waterfowl, you are also going to want him to take a path across the water to do the same. You want him to avoid the shore and go right into the water. The next step is to toss the bumper even further in the water. Each time you practice this training technique, you should toss the bumper a little bit further into the water so that he will have to swim to get it. He will soon get used to using this path.
You can then use a launcher to toss the bird all the way across the water so that it ends up on the land. You must break your dog of the instinct of going around the shore to retrieve and taking the shortest path, which is through the water.
When you are trying to shore break your retriever, you should make sure that the water that you are training your dog in is deep enough to that your dog cannot touch bottom. Retrievers know how to swim instinctively and this will enable him to learn how to jump right into the water to retrieve instead of trying to go onto the shore where he can touch bottom. If swimming water is not possible, try to cover up the shoreline as best as you can with grass and other objects so that he has to jump in.
It may take you a few tries to shore break your retriever. You do not have to have all of the lessons in one day. The objective of this is that your retriever will take the shortest distance, despite what he sees as an obstacle, to get to the bird and retrieve it for you. This will make hunting more effective for you and eventually, the dog will be able to even jump from a boat without hesitation to retriever waterfowl, making him an excellent hunting companion to have along with you when you are hunting ducks, geese and other waterfowl.