But the purists may want to get used to their paddling cousins. Like snowboarding, SUP doesn't look like it will vanish with the next swell. "It's not a fad -- it's already sticking," says Matt Warshaw, author of "The Encyclopedia of Surfing."
On average, waves at Malibu's first point, arguably among the best on the West Coast, provide rides that range from 5 to 10 seconds. When you consider that several dozen surfers usually vie for each swell, you can begin to understand the arithmetic behind the animosity.
Moreover, just having someone slashing around in the surf with a paddle, and already in the standing position before a wave even breaks, further irritates traditional boarders, who spend most of their time laying idle on their bellies.
Surf shops up and down Southern California's coast are selling stand-up boards and offering lessons. The problem is that SUP riders with little or no surfing experience don't understand the etiquette of the water.
"SUPs will pull into a wave with their paddles right in front of you, and you're like, 'really, did that just happen?'" Mr. Walker says. "Too bad there isn't a bike lane for stand up surfers."
Yet not all SUP riders are new to the sport. In fact, the roots of stand-up surfing reach back more than 100 years ago, when wave riders in Hawaii were using paddles and wood planks for transportation. Some surfers even believe that today's version of stand-up surfing echoes the practices of the ancient Polynesians.
"SUP is a throwback to what true watermen all aspired to do, and once you try it, you're instantly hooked," says Scott Bass, a San Diego surf talk radio host. "But it's also a curse."
Mr. Bass, who prefers stand-up surfing when the waves aren't big enough for shortboarding, says SUP is like having too much of a good thing.
"People see stand-up riders catching waves and suddenly they're everyone's enemy," he says. "There are some beaches where there's such a negative vibe that stand-up surfers don't even step foot in the water."