Some dogs take right to the water. They are curious and push their paws around. Sooner or later they will slip and they will find they are well equipped to swim and that is what they do. A Labrador retriever is bred for swimming. It usually comes quite natural to them. However you will find the rare Labrador who simply does not like the water. Dogs have personalities just as humans do. If you happen to have a dog that does not like the water, it is best not to force the issue. However, you can train a dog to swim and tolerate the water even if he doesn’t care for it.
To train a dog to swim, you simply expose the dog to the water for periods of time insuring she understands her commands. To insure she does not get over tired, you can equip her with a life vest. Make sure she has plenty of drinking water as the excursion may take a lot out of her. Watch for signs of heat exhaustion and dehydration and deal with them quickly. Do not let the dog suffer in the heat. She will need to trust you to get over her reluctance to get in the water.
Of course you can always start out with a back yard kiddie pool and let your dog explore on its own. Just like children, teach them early for the best results.