My dad is a disabled veteran and would like to try kayaking. is this possible with the use of just one arm?

Let's consider this: 1. What's his general health like? 2) how would he do if the boat tipped over? (of course, you wear a life jacket! but it still can be scary.) 3) does he want to do this? 4) does he have other disabilities? Then, i'd see about getting a triple kayak with an experienced kayaker fore and aft, and have your dad paddle in the middle. But keep in mind, this is water! drowning is a risk. Good luck.