Before you go swimming with your dog, you should play around the water first. This is particularly important if you are unsure about whether or not your dog loves the water. There are many water-loving breeds, but not all dogs of these breeds will actually enjoy being in the water.
To help your dog adjust to the water, you should throw a ball for them to chase in the shallow areas. This will help your dog associate the water with fun. If your dog is still unsure about the water, you should try a few play sessions to clam them.
You should also allow your pet to walk around the perimeter of the water while they are on land. This will help them assess everything and help them understand what is waiting for them. You should wait until your dog shows signs of being happy and relaxed around the water before you attempt anything. Trying to swim with an uncomfortable dog can cause a fear of water which takes years to deal with.