Dogs are much like people when it comes to swimming.
Some dogs and people take to the water easily, swim with no problems, and are comfortable in the water. Other dogs and people are more worried and need some help learning to swim.
With dogs, there are also some breed characteristics that affect whether the dog will be a good swimmer. Newfoundlands, Portuguese Water Dogs, retrievers, and spaniels were all bred to be comfortable in the water, as it was a part of their original occupations. Newfoundlands were water rescue dogs; Portuguese Water Dogs helped fishermen, and the retrievers retrieved birds from both land and water. On the other hand, Bulldogs and Boxers both with their short muzzles, muscular builds, and lack of body fat, even when they enjoy water, have trouble swimming. Then some individual dogs just hate water. While my two younger dogs love water, my eleven year old Australian Shepherd, Bashir, sees no reason why his paws should ever leave the ground and paddle in water. Since he's made it plain that swimming is not for him, I don't force him.
Before beginning any swimming lessons, start by playing in or near the water. Throw the ball or toy, let your dog splash in shallow water (even a big puddle) and let him associate water with fun. If your dog has some reservations about water, have several play sessions like this until he's comfortable with the splashing.
Choose the Location
The ideal place to introduce your dog to swimming would be a place with an easy slope into clean quiet water with no current, and where you can go into the water with your dog. Although some dogs will willingly jump into the Pacific Ocean surf, this isn't always the best way to teach your dog, and many dogs have been frightened in rough surf. A quiet pond, lake or lagoon with clean water is better.
Life Jackets are Great
Fit your dog with a canine life jacket before going swimming. Not only will this provide you with a handle over the dog's back to save him if needed, the life jacket also provides some additional buoyancy. This will give your dog some confidence as he'll ride higher in the water. Let your dog wear the jacket at home a few times, then out for walks, and when he doesn't pay any attention to it, then begin swimming lessons.
In the Water and Back Out
Your dog needs to know he can get out of the water before his feet begin paddling. Not only is this a safety issue but it's another confidence booster. With a leash on your dog, walk him in enough so his paws get wet as you encourage him, "Let's get wet! Yeah! Awesome dog!" Then turn around and both of you dash out of the water, "Get out! Come on, good boy! Get out!" Praise him when he's out of the water. Then do it again, making a game out of walking into the water and dashing back out.
Use a Ball or Toy
Standing in the water, toss a favorite ball or toy that floats in shallow water and encourage your dog to go after it. Praise him when he does, telling him what a wonderful dog he is. As your dog gains confidence splashing in the water and retrieving his toy, then toss it slightly deeper until he begins to paddle. If he looks worried, go walk or swim next to him, guiding him out of the water while praising him. If he panics, use the handle on the life jacket and help him to shore. Then begin playing in shallow water again before tossing the toy deeper.
The most efficient way for your dog to swim is with his front feet paddling under water without splashing. A good canine swimmer moves through the water with his head out, breathing easily, with no splashing. Many dogs, however, when first learning tend to try to frantically grab onto the top of the water. If you can walk or swim next to your dog, calm him, support him gently, and then praise him when he calms enough to stroke more slowly without splashing. This takes practice just as human swimmers need to practice their skills.
Swimming Pool Tips
Have a visual guide (such as a large potted plant) at the steps so your dog knows where he can get out of the pool. Most drowning occur when a dog goes to the side of the pool, tries to climb out, can't, and then becomes exhausted. Have your dog walk into the pool next to the plant, and then help him get out at the same spot. During every pool session with your dog in the water, move your dog around the pool and from different locations, point your dog to that plant and help him out there. Even once your dog is a proficient swimmer, don't let him go in the pool without you.
Stop each swimming lesson before your dog gets physically or mentally tired. If you ask him to do too much in a session, he'll learn to dislike this new activity. So keep the lessons short and fun.