No. Your cool.
Cannabinoids aren't water soluble (as in they don't dissolve into water). This is the principle that bongs work on. The tar and gunk gets trapped in the water, and the cannabinoids move through the water to your lungs.
Cannabinoids DO dissolve in alcohol, which is why you can make 'green dragon' which is essentally cannabis infused grain alcohol.
So no, you will NOT loose potency vaporizing through a bong AS LONG as your using just water!
Happy medicating!