I walk everywhere, from aquatic to terrestrial environments.
That is great for your health I'm sure!  Do you enjoy being out in nature while you are walking?
I do, but it raises different problems than that in water, I get tired very easily!
Well, if you keep at it, you will build up stamina to last longer, right?
You're right, but walking, running, or jumping cause pain in my knees, sadly.
That's no good.  You should go to the doctor and get it looked at.  They may be able to do something to ease or eliminate the pain.
I probably should but I am scared of the use of chemicals that I a doctor might do.