Swimming is great exercise. Dogs need daily exercise but they need stimulation more than anything. They need to get out into the world to smell smells and hear noises. They need their senses stimulated. Keeping your dog locked in a yard or house is just cruel and a recipe for trouble down the track. Not giving your dog enough stimulation leads to destructive and anxious behaviour. Between 3 and 5 years old dogs start to present with issues that their owners say " He/she used to be ok". This is not the case it has just built up and now the dog has matured it is reacting. An untrained dog is an unknown dog and an unknown dog is a danger to itself and sometimes even those around it.