Barefoot, of course, the man who has for two decades told us which beach is best stood on the soft white sands of Fort De Soto Park and explained to five TV cameras how it all works."Scientifically," he told them.Stephen P. Leatherman, a professor at Florida International University, is more famously known as "Dr. Beach." His website boldly proclaims him "America's Foremost Beach Expert," and on his business card photo, he is standing on a beach wearing a Hawaiian shirt, sugary sand cascading from his fingers. He has officially ranked beaches for more than two decades.He came to the area this week for the Association of American Geographers' annual meeting, being held in Tampa. On Friday afternoon at the park, just before helping lead a group of the geographers on a tour, Leatherman met with reporters.Fifty criteria, he explained, determine his annual best beach rankings.Water and sand quality are key, he said. Safety counts, too. He doesn't approve of rip currents or drownings, and buried cigarette butts are also costly. Amenities, width and parking also matter."I have to count off if you bring dogs to a major beach," he said. "I'm afraid not everybody cleans up, and I'd have to take off for that."Also, clean bathrooms," he said. "Come on."In South Beach bathrooms, for instance, Leatherman said he had to hold his nose."It's awful, you know?"He spoke of Fort De Soto's beach, however, with reverence. In 2005, he named it the country's best. After a beach reaches the Dr. Beach summit, he explained, it's "retired" to make room for others.Leatherman, 66 and a lover of sand since childhood, said on Friday that starting in 2015, he would again consider past champs.Asked why the same beaches aren't always ranked in the same order, given that (to those who don't specialize in judging such things) they don't seem to change much from one year to the next, Leatherman insisted they do change. A lot."I keep up with all the beaches. I try to visit them all regularly," he said, noting that a friend in Hawaii sends him photos on the years he can't make it there. "I stay up on beaches and, you know, if a beach has a bad year, which all beaches can have a bad year or a bad day, if they had some stormwater overflow from torrential rains, I had to knock some of those beaches back, okay. When we had the oil spill, I had to knock some of the beaches in the Panhandle back, all right. Although this area, I kept it up because I said the oil spill is not coming to Southwest Florida, and it didn't."After the news conference, several TV reporters, apparently disappointed that he wasn't judging the park's beaches, asked Leatherman to simulate the process.He walked to the shoreline and picked up a wad of sand. "Very fine," he said. Good enough to earn a 4.5. He gave the color a 4, adding that the water quality was "very high."He looked up and squinted at the dunes. Normally, Leatherman said, he would use a laser to measure the beach's width, but he guessed it was around 150 feet. At least a 4.Dr. Beach seemed impressed.