In short, duckwater is pre-cum.
For long (?), when a guy's got a boner, the tip of it gets wet on it's own with a fluid that is not cum, but has been known to impregnate as it can contain traces of semenosioflous (aka semen). This fluid is sometimes called pre-cum.
She watched the single drip of duckwater come out of his dick hole - and licked it.
