Also known as the female clitorus, it's metaphorically equivalent to a frightened lady in a sea vessel of some sort. The shape of a boat shares a distinct similarity to that of a cooter. When the little lady stands up in the boat that is when the female clitorus is excited and this often brings about an orgasm.
"I tried for hours, rocking the boat about, back and forth, but I couldn't get the little lady in the boat to stand erect."
by Cooterscooter January 14, 2009