Calculating Attendance at the I.B. Sandcastle Festival

Hi Matthew:
I read that the Sandcastles Festival here in Imperial Beach had over 400,000 visitors during the three-day weekend, more than any previous festival. Any clue how they can possibly calculate that figure and how precise they are able to be in their calculations?
—Donna

Attendance figures were provided by the Imperial Beach lifeguards. Their method is best described as an “informed guess” inasmuch as there’s no real way to count the people who visit the beach. Lifeguards are out there all day, every day, looking at the ocean and watching the swimmers, boaters, surfers, and sunbathers ebb and flow like human tides. If anyone’s in a position to guess correctly, it’s the lifeguards. To them, the beach is a regular, predictable environment that has its patterns and rules. They can read a busy beach the way meteorologists look at those swirly doppler radar pictures and discern meaning from the chaos. By the by, the IB lifeguards rescued over 300 people last year and nobody drowned on their watch. Kudos.