What Happens with a Splash of Water in Scotch?

A woman celebrating her 80th birthday on a cruise ship orders a Scotch with two drops of water. The bartender offers her a drink on the house for her special day.

After finishing the drink, another woman beside her offers to buy her a drink as well. She requests the same drink again. Then, a man on her other side also offers to buy her a drink. She requests the same once more.

When asked why she only adds two drops of water to her Scotch, the elderly woman humorously explains that at her age, handling liquor is easy, but managing water intake is another story.