0_Apprentice
I think I am going to start swimming for exercise. I used to really enjoy it when I was younger.
1_Wizard
That's a good idea. Since swimming is the self-propulsion of someone through water, it burns a lot of calories.
0_Apprentice
That's good to know because I need to burn A LOT of calories. I need something more low impact for my knees too.
1_Wizard
The elliptical trainer is also good for low impact. It doesn't cause excessive pressure on the joints.
0_Apprentice
That's a good idea.  I wonder what swimming stroke would be the best for exercise. 
1_Wizard
I'm not sure but there are so many different strokes I"m sure you could figure out which one.
0_Apprentice
How do we not even sink when we swim? It's fascinating to me.
1_Wizard
When you swim you use locomotion. It's achieved by the coordinated movement of arms and legs.