Buzz is my first dog, and his personality is a textbook Labrador. One of the first things he learnt naturally was to fetch the ball. He responds to the ball so well, that I taught him many tricks of his tricks by throwing the ball as positive reinforcement, instead of treats/food.
One of my buddies has a yellow lab as well, and suggested we take the dogs to the local pond. Buzz, around 3 years old at the time, to my amusement knew exactly what to do to float and swim!
They both had a blast, and we made things interesting by throwing one ball between the two of them.
Here are some pictures from that day (shot with a D7000 + 55-300mm lens)