Puppies learn to swim easiest if you teach them sooner than later.  Puppies go through several fear stages.  The first is from about 8-11 weeks of age.   The second starts at around six months.  The best time to teach a puppy to swim is either before he’s 8 weeks old or between these two stages.  If your puppy happened to be born in the fall and you want your puppy to swim, I’d teach him before he was six months even if it was cold.  Your puppy won’t mind the cold even though it won’t be comfortable for you to get in the pool with him.  I’ve had dogs choose to swim when the temperature was close to freezing.

To teach swimming, begin by luring your puppy with food and toys into a small kiddie pool filled with a few inches of water.  Get them gradually used to walking around in the water and then gradually jumping in and out.  For a timid dog, you may need to feed them their whole meal as lures in the pool.  Work daily with your puppy in the kiddie pool until they are playing comfortably in it.

Then move to a real pool.  Start on the steps.  You get on the first step.  Pick your puppy up and put him on the first step with you and pet him and give him a treat.   He’ll probably climb back out.  That’s okay.  Try luring him with the food back onto the first step himself.  If your puppy won’t take a treat because he’s too stressed, don’t push it.  Go back to the little pool for a few more days..  If he’s a little stressed but still eating, then you’re ok.  Don’t force your puppy in the water except for putting him on the first step gently and letting him crawl back out.  Continue trying to lure him to the first step himself.  If he doesn’t come, then pick him up and put him there and treat him again.  If your puppy is continuing to eat, push him a little further.  Try luring with a favorite toy or ball.

When your puppy is fairly comfortable on the first step, the next step is to carry your puppy in the water.  Feed him while you are holding him.  If your puppy is eating, he’s not overstressed.  At this point, you need a second person to sit on the step while you carry your puppy out a few feet into the water. Encourage your puppy to swim to the person on the steps.  Do this several times a day for several days.  Then after putting your puppy on the first steps, try throwing a ball out just a couple of feet away from the step and see if your puppy will swim to get it.  Gradually increase the distance you are throwing the ball, always making sure that you are calling your puppy back to the steps to get out.