Not all dogs can swim and some may require positive reinforcement training to get used to the water.
Do not throw your dog from a dock or boat, as this will likely scare him from ever entering the water on his own again. Instead, use encouragement, toys, treats to make him feel safe. In gradual steps, you may be able to acclimatize your dog to water.
Carry small dogs into the water if they are not too upset by this. Once you are deep enough that swimming is possible, point your dog’s nose to the beach and have someone call him back to shore. This way, the dog learns that his feet will touch the ground if he just swims toward land.
AT THE POOL:
Never leave your dog unattended in or around a pool. When the pool is not in use, it should be fenced off, covered, or your dog should not be allowed access to the area.
There should be a wide ladder or stairs for your dog to use to exit the pool and you must train him to use these. Not only is this a safety issue, but if his nails punch holes into the pool liner, it will be an expensive accident!
Always rinse chlorinated water off your dog. This can irritate the skin, as well as the stomach if he drinks it or grooms his wet fur.
Strong currents or undertows can drag your dog far from shore. Often, dogs become so focused on retrieving a toy from the water that they can easily drown. Make sure your dog has a good recall command (comes when he is called back to shore).
There are flotation devices made just for dogs in a variety of sizes. If your pet is going to be spending a lot of time around a pool, open water, or boating, a life jacket may be a good investment.
While boating, you may want to keep your dog restrained, using a short harness. If your dog is leaping around a boat, he can knock people down or overboard, upset the entire vessel, or jump into the water. Many injuries can occur as a result of a dog swimming into a turning propeller.