A citation from the movie The Town:
And one of the guys told me that... to walk until I felt the water on my toes. It was the longest walk in my life. I kept thinking I'd step off a cliff. And then I felt the water.
Why is it the water and not just water? Any water feel alike. They could have gone with just water. There is no possibility that you feel some water on your toes and say: "No, it is not that water I was told about, I should keep going until I feel the water."