Sorry , I did not mean to scare you. Yes, don't use it in the bathtub or in the swimming pool, hot tub etc. That is just common sense. Just use it as your son instructed you and do the 7-20-7-20-7 minute sessions that Dr. Clark recommends and see if you feel any reactions. If you have not tried it yet, you probably will not feel anything in your hands. I have used it as a zapper but I can not say that it did work or that it did not work. I will have to experiment with it some more. I want to try different frequencies to see what happens. I have made one Zapper that was a variation of Clark original design. It used a lower frequency. The first 7 minutes made me feel a bit dizzy and I could feel a sensation in my hands. I want to try and duplicate that with the function generator to see if I get the same reaction.
I do use a Clark Zapper that I made from her book. It seems to work very well. I think I read somewhere in one of her books that she used a frequency generator as her first Zapper. I am not sure what the difference is between a frequency generator or a function generator. Maybe your son would know. I have one of the ones pictured in her book.

Maybe you could talk your son into making you a Clark Zapper. He should be able to make one fairly easy.