How much time does it take to replace a water pump?

I have a 1987 Toyota Corolla. Someone told me that a water pump on my car could be replaced in as little as 1/2 hour! Is that true?How much time does it take to replace a water pump?Is this a 4 cyl or a V6? A 4 cyl will take about an hour, a V6 about 2 hours.