Chemical composition Puns

Because it barium

So my daughter was filling out a form that was asking if she has left the country recently. Well, technically she has. She took a canoe trip over the border into a wilderness area.

I told her that since she didn't go to any populated areas or contact any wildlife that she could just say no. She argued and said "Well, i mean i did come into contact with Canadian water and land."

I said, "Well, that's different. You know Canadian water has a different chemical composition, right?"

She just looked at me.

"Yeah, it's H2O A?"