Can I get you anything?

Generally, I prefer water to soda, juice, milk, scotch, root beer floats, whatever else might be offered. But in a restaurant, here's the scenario:

        

w-a-t-e-r

I order water.

The waiter looks up, "Are you sure?"

Am I sure? Does he ask that when someone orders a Blue Margarita?
 

Accommodating him, I reconsider—Do I really want water? 

"Yes, I am sure," I say decisively. "Just water." 

"Did you want bottled water?" 

"No," I say.

i don't want a lemon in it either, thanks