SAN DIEGO—Consuming alcohol is illegal on this city's famous beaches. But, thanks to a loophole authorities are now trying to close, drinking a few feet from shore is not. 
 
 That's why, this past Saturday afternoon, Jon Kraemer sat atop an inflated air mattress, sipping a Bud Light he pulled from a floating cooler. 
 
 The 26-year-old pharmaceutical salesman was tipsy and carefree and dangling his feet in the water, despite the dozen police officers standing on shore making sure no booze was consumed on land. 
 
 Floatopia -- A Utopia? View Slideshow Sandy Huffaker for The Wall Street Journal Beachgoers on rafts clogged the water off of one San Diego beach July 17. 
 
 "This is the best day ever, that's all I have to say," said Mr. Kraemer. 
 
 San Diego's float parties are a case study in the law of unintended consequences. Fed up with litter and drunkenness on its beaches, San Diego's city council in 2007 passed a one-year ban on beach drinking. Voters made the ban permanent a year later. But there was an oversight: The ban defines "beach" as "the sand or land area bordering the water of an ocean or bay." The wording inadvertently created a drinkers' haven in the water. 
 
 Dozens of large and small drinking-and-floating events have been held since mid-2008. Many of them, including last weekend's, are organized anonymously through Facebook, the social networking site. 
 
 Police say that when the parties started, they checked with the city attorney's office about whether they were legal. It concluded that, indeed, drinking in the water isn't the same thing as drinking on the beach. "If you're floating, you're good," says Chris Ball, captain of the San Diego police department's northern division. 
 
 But the days of boozy float parties—dubbed "Floatopia"—may soon be over. The council's public safety and neighborhood services committee recently passed a proposal to amend the drinking ban so it extends to "bathers," a category that includes almost anyone not in some sort of boat, including kayaks and canoes. On Monday, the full council is expected to vote on making it "unlawful for any bather to consume any alcoholic beverage within one marine league of any beach." A league is about three-and-a-half miles. 
 
 "Now we have to take [the alcohol ban] a step further," says Tony Manolatos, a spokesman for city councilman Kevin Faulconer, who represents several of San Diego's beach communities, including Ocean Beach and Pacific Beach. 
 
 San Diego isn't the first beach community to grapple with Floatopia, though the city's parties are unique in that they were created purely to dodge the law. Santa Barbara County, which had been dealing with float parties since 2005, last year banned alcohol on Isla Vista beach and 100 yards into the water. 
 
 San Diego's parties are held in small bays that extend inland, rather than the city's miles of oceanfront. In the bays, calm waters and the absence of waves facilitate Floatopia drinking. Most floaters congregate right off land in water just a few feet deep. 
 
 The largest Floatopias have attracted roughly 3,000 floaters, many of whom drink way too much. As the day wears on, beaches fill up with trash, beer cans and weary drinkers napping on slowly deflating rafts. 
 
 Extra police and lifeguards cost the city tens of thousands of dollars. 
 
 "If you slip off and the first deep breath you take is seawater, chances are you're not coming back up," says Capt. Ball. "That's what we're concerned about." Nobody has drowned so far. 
 
 Most of San Diego's Floatopias happen in and around Pacific Beach—known as P.B.—a young, raucous neighborhood of bungalows and a two-mile-long strip of bars that ends at the Pacific Ocean. Back when beach drinking was still allowed, P.B.'s Fourth of July celebrations had so many alcohol-related arrests that police brought in a recreational vehicle outfitted with temporary jail cells. 
 
 The alcohol ban has calmed things down. On July 4, the mobile jail got little use and won't be returning next year, Capt. Ball says. "The beaches are just tranquil now," says Jerry Hall, a Pacific Beach resident who favored the alcohol ban. 
 
 The water, however, is a different story. Booze abounded at last weekend's Floatopia. Floats ranged from a barely buoyant blow-up doll to an inflatable deck that hosted a small dance party. Floating tables made possible games of "beer pong," a drinking game in which players toss ping-pong balls across a table hoping to dunk them in opposing cups. 
 
 Kim Rampaul, 24, came with a two-seater float that has dual cup-holders and a built-in cooler. Mr. Rampaul, a college student and Floatopia veteran, was lathered in sunblock and brought along beer, snacks and Gatorade. Like most floaters, Mr. Rampaul uses rope to tie his float to friends' floats, creating a bobbing lounge. 
 
 "It's just fun that we're allowed to do this," he says. "It's like you can't touch us, we're in the water." 
 
 San Diego's Floatopias have murky origins. One of the first people to publicize the loophole was Bradford Boyle, then an information technology engineer, in mid-2008. Mr. Boyle, 28, had been told that drinking in the water was a way of dodging San Diego's now-defunct rules prohibiting drinking on the beach before noon. Later, when the broader alcohol ban was passed, Mr. Boyle figured the same logic could be used to legally drink near but not on the beach. 
 
 After confirming the loophole with police and lifeguards, he shared the discovery on a personal website, and the idea spread. Mr. Boyle is now pursuing an M.B.A. degree and says he isn't organizing Floatopias any more. "It's just gotten out of control," he says. 
 
 Perhaps surprisingly, that view is shared by a number of Floatopia participants. Mr. Rampaul, for instance, says that despite his love of drinking and floating, parties have gotten so big, the city council had to extend the alcohol ban into water. 
 
 "Unfortunately, it makes sense," said Mr. Rampaul last weekend just before hopping on his float and enjoying a few beers. "Floating? Drinking? That's just not going to work out." 
 
 Write to Conor Dougherty at conor.dougherty@wsj.com ||||| The San Diego City Council on Monday voted unanimously to ban drinking on Mission Bay in an effort to stop the "floatopia" booze parties that have exploited a loophole in the city's ban on drinking on beaches. 
 
 Police and lifeguard officials told the council that the "floatopia" parties, at which hundreds of college-age people drink while floating on rafts, inner-tubes and other devices, are a menace and could lead to drownings because of drunkenness and injuries from broken bottles. 
 
 But opponents of the ban said that further limitations on drinking could hurt tourism. The council was not swayed by that argument. 
 
 "This is not the San Diego City Council saying no-no-no to things," said Councilwoman Marti Emerald. "This is the San Diego City Council trying to keep people alive at our beaches." 
 
 After an alcohol-fueled riot on the beach at Pacific Beach during Labor Day weekend 2008, the council voted to impose a one-year ban on alcohol consumption on city beaches. In November of that year, city voters approved a measure to make the ban permanent. 
 
 But the ban did not cover drinking in the water. Monday's ban on drinking in the water is set to become effective immediately. The ban does not include drinking on boats. 
 
 -- Tony Perry in San Diego 
 
 Photo: "Floatopia" party on Mission Bay. Credit: Nelvin Cepeda / San Diego Union-Tribune
– San Diego's city council has closed a loophole that allowed partygoers to dodge a ban on drinking on the beach by boozing just offshore instead. Wording in the original ban defined beach as land only, leading to "Floatopia" parties which saw thousands of people drinking on rafts and inner tubes just a few feet offshore, the Los Angeles Times reports. The updated law now says "bathers" need to be one marine league—around 3.5 miles—offshore before they can drink alcohol. City leaders say the floating parties were a disaster waiting to happen, and even partygoers say the law probably isn't such a bad idea. "Unfortunately, it makes sense," a college student taking to his air mattress for a final few beers told the Wall Street Journal. "Floating? Drinking? That's just not going to work out."