“WAVES are just a little part of surfing,” the big-wave surfer Kala Alexander said last week as fat cumulus clouds drifted through the sky above the North Shore in the US and an ocean both brilliantly turquoise and yawningly flat. “You have to understand what it means to be a waterman,” he added. “You have to understand the way of life. You have to have respect.” With the shift from the moody wet winter Hawaiians call ho'oilo to the drier season known as kauwela, the swells that have made this stretch of coastline a famous surfing destination have all but vanished. By mid-May most of Oahu's celebrated big-wave riders are elsewhere on the planet, satellite-tracking five-story waves off the coasts of Tahiti or Chile or Peru. So this is downtime at Velzyland, Backyards, Log Cabins, Pipeline, Chun's Reef, the Banzai Pipeline, Kammieland, Gas Chambers and Sunset, legendary surf breaks whose names evoke the recent history of a sport devised here an eon ago and once known by the gentle-sounding term “wave sliding.” Not much about surfing nowadays bears any resemblance to the recreation practiced on koa wood boards by ancient Hawaiians — not the boards or the apparel or the attitudes or the stakes. Four decades after “The Endless Summer” universalized the romance of an easygoing nomadic life, technology has radically changed surfing by making it accessible to the masses. Marketing has turned what was once a niche pastime into a $7.48-billion surfing-goods industry. And the easy bonhomie that was Hawaiian surfing's public face has been supplanted by something more ugly and fierce, with surfers competing not just for prize money but for territorial rights to an increasingly crowded sea. Although little about localism or surf territorialism is new, the public was mostly unaware of how violent the battles fought between locals and outsiders over popular breaks have sometimes become. That was before YouTube, where the keywords “North Shore beat down” summons up videos of bloody skirmishes between surfers like Mr. Alexander and putative interlopers; before films like the indie documentary “Bra Boys,” released in April, noted the resemblance between certain surf clubs and street gangs; before the well-publicized San Diego murder trial of one such alleged surf gang; before the band The Offspring wrote a song about the perils of crossing locals from the North Shore club called Da Hui; and before the club referred to in the song gave rise to a cult clothing line. With annual sales of roughly $2 million, the privately held Da Hui is a flyspeck in comparison with mass-market behemoths like Billabong or Quiksilver. But the appeal of the label — now sold at surf shops in 19 states and 12 countries — is that its black boardshorts and no-frills logos both bypass the sport's floral sartorial clichés and also, for those in the know, summon up a hard-core, roots surfer image of riders like those Da Hui underwrites. Formed in 1976 as Hui O He'e Nalu, Hawaiian for Club of Wave Sliders, by the surfer Eddie Rothman and his friends Bryan Amona, Terry Ahui and Clyde Aikau, the club's evolution and that of the brand it became paralleled other major changes in the sport. Surf breaks along the rural Oahu coastline were little populated in the 1970s. Contests were limited and largely invitational. Now when the winter swells roll in, the North Shore is mobbed. The year-round population of 18,300 more than doubles as squadrons of surf transients from around the world drop in at beaches that can become as crowded as the north coast's single two-lane highway. As early as the mid-1970s, locals began taking notice of this influx and its effect on the waves in their backyards, and instituted a kind of militant aquatic traffic control. “We don't just go out in the water and kick people out,” said Mr. Alexander, a pro surfer with looks so keenly photogenic that they, as much as his wave-riding talent, have won him a passel of sponsors, as well as a part in “Forgetting Sarah Marshall,” a role in “Blue Crush,” a lavish pictorial shot by Bruce Weber for Italian Vogue and an unfortunate starring role in a YouTube video in which he and a buddy are seen beating an unlucky blond surfer to a bloody pulp. “We're just sticking up for our beliefs and our neighborhood and our families,” Mr. Alexander said at a barbecue Mr. Rothman held at his oceanfront house near Haleiwa last week. “People ask, ‘Where's your aloha?' ” Mr. Alexander explained. “The aloha spirit was burned right out of Hawaiian people.” Keali'i Mamala, also a surfer, was a guest. There was “plenty aloha,” as people here say, in evidence that day. Friends dropped by Mr. Rothman's house carrying blister packs of hot dogs, bags of chips and platters of home-sliced sashimi. Mr. Rothman's two pit bulls scooted around underfoot; his young son gutted and grilled some fresh line-caught fish. Keali'i Mamala, who a year ago was captured on film riding a monster wave at Mavericks, the legendary surf break in the frigid waters off San Francisco, quietly flipped burgers on a grill. One of Mr. Rothman's friends came by with three teenagers from a local Ronald McDonald House, where they are staying while being treated for cancer. The scene was so low-key and clannish that it was difficult to link some of the guests at the party with newspaper accounts of the less savory aspects of their reputations. For instance, Mr. Rothman was charged in 1987 with extorting surf-meet promoters and holding “the North Shore in a state of feudalism for years.” In 1999, Mr. Rothman, often called Fast Eddie, was arrested again on charges of first-degree burglary, kidnapping and extortion, as he and two friends were accused of barging into a Sunset Beach home and threatening the residents with death if they failed to turn over a truck. Mr. Rothman was acquitted in both cases. Four people were beaten in the truck incident, and yet not long afterward a Hollywood producer proposed to Mr. Rothman that they collaborate on a cinematic picaresque about his eventful life. Born in inner-city Philadelphia, he was raised in Southern California until, as he says, “my parents threw me out at 13,” Mr. Rothman fetched up in Hawaii, where he was raised by foster parents and went on to a variety of pursuits, surfing the most mainstream among them. “I said forget about it,” Mr. Rothman said, referring to the movie deal. “I don't need anybody making a movie about me. I've been on television enough.” When Mr. Rothman first formed Da Hui, his goal was ostensibly to preserve not just turf but what was Hawaiian in a Hawaiian-invented sport; the club's logo was taken from an ancient surfer petroglyph. Unlike many of Da Hui's members, Mr. Rothman is not of Hawaiian descent, but then, identity is a flexible thing on these islands, where most people consider themselves hapa, or half, of some race and can easily diagram the component parts of their ancestry Mr. Alexander, for instance, was raised on Kauai and looks Hawaiian, an impression he augments by covering himself with talismanic Polynesian tribal tattoos. In truth, he said, “I'm hapa haole,” or half-white. “My mom was a blue-eyed blonde from Detroit.” Particularly as Hawaii experiences a renewed wave of development (the median house price on Oahu is now about $650,000 and one of the largest development projects in Waikiki's history recently turned eight acres there into a mid-Pacific Beverly Hills), the emphasis on roots culture has intensified. It is not just that there are more incursions on renowned North Shore surf breaks; after all, as Hans Hedemann, a legendary pro surfer who operates surf schools on Oahu, said, “For good surfers, there's always plenty of waves.” It is that the pressure has intensified on Hawaiians to define and claim their identity and what they think of as their space. But while graphic slugfests draw hits on YouTube, localism does not sit well with island officials. “We don't condone it at all,” said Lester Chang, the director of parks and recreation for the city and county of Honolulu, which encompasses the island of Oahu. “I am not aware of any incidents occurring during the three years that I have been director,” he added. “But it would be very disturbing to us,” if people were excluded from surf spots based on “their racial origin or the color of their skin.” Anyway, Da Hui has mellowed, “now that a lot of the original guys are grandfathers,” said Mahina Chillingworth, the vice president of the board of the 400-member club, which sponsors annual events, like beach cleanups, more likely to be associated with the Elks than with a club with Da Hui's reputation. “Hui O He'e Nalu started,” explained Ms. Chillingworth, who is also a liaison with the California company that manufactures Da Hui clothes, “because local people were getting real disrespected, and outsiders were coming here and looking at Hawaiians as aborigines.” These days the black boardshorts that once signaled territorial assertion are sold at Costco, presumably to consumers innocent of their original intent. – NYT __