Scotch with two drops of water

Scotch with two drops of water.
A lady goes to the bar on a cruise ship and orders a Scotch with two drops of water. As the bartender gives her the drink she says, " I'm on this cruise to celebrate my 80th birthday and it's today."
The bartender says, " Well, since it's your birthday, I'll buy you a drink. In fact, this one is on me."
As the woman finishes her drink, the woman to her right says, " I would like to buy you a drink, too."
The old woman says, " Thank you. Bartender, I want a Scotch with two drops of water."
" Coming up," says the bartender.
As she finishes that drink, the man to her left says, " I would like to buy you one, too."
The old woman says, " Thank you. Bartender, I want another Scotch with two drops of water."
" Coming right up," the bartender says. As he gives her the drink, he says, " Ma'am, I'm dying of curiosity. Why the Scotch with only two drops of water?"
The old woman replies, " Sonny, when you're my age, you've learned how to hold your liquor. Holding your water, however, is a whole other issue."