I have to say that the dog had no intentions whatsoever to jump into a underwater treadmill and exercise out of his own will or determination. On the contrary the dog has no intentions whatsoever to work that butt out, all he wants to do is eat and eat, and then eat some more. What you will see in the video below is called hydrotherapy, and it is good way for pets to recover after a muscular injury. The therapy is a great way for a dog or a cat to strengthen the muscles after an accident. And of course it is also a way for your pet to lose weight too.
But since the professionals can easily understand the determination of dogs to exercise, they decided to incentivize him on exercising. They came out with a genius idea that included food in it. The video below will better explain the genius idea that the professionals came up with.