0_Apprentice
I really enjoy swimming!  Do you like to swim?
1_Wizard
Yes I do! Swimming relies on the buoyancy of the human body. 
0_Apprentice
What do you mean by buoyancy?  I am unfamiliar with that term.
1_Wizard
Buoyancy causes the body to float.
0_Apprentice
I see!  Is swimming good for exercise?
1_Wizard
Yes it is. And it's better on the body then some other exercises, since it is considered low-impact. 
0_Apprentice
That is good to know since I have bad knees!  I heard that babies can be born in water and are able to swim!  Is that true?
1_Wizard
Yes, they can! It has do with the fact that humans can hold their breath under water. It's an evolutionary response. 
0_Apprentice
Fascinating!  What is the longest distance a human has swam?
1_Wizard
139 miles. It took him over 50 hours to do. 