NEW YORK — When the tide rushes into New York Harbor, a strange thing happens at the Gristedes supermarket on Roosevelt Island. The freezers, cash registers — even the red neon "Bagels" sign — hum with electricity from the rip coursing up the East River.

The power comes from six underwater turbines bolted to the river bottom by a little-known startup called Verdant Power LLC. Their 7-foot-long blades turn, silent and out of sight, until the flux crests. When the tide turns, the contraptions pivot 180 degrees and make juice on the ebb.

Tiny Verdant has a rich and famous partner, billionaire hedge fund manager Paul Tudor Jones. His Tudor Investment Corp. has staked $15 million on New York-based Verdant, a company with 20 employees, zero profit and one very aggressive competitor lurking just upstream.

From New York Harbor to San Francisco Bay, a new breed of green-energy entrepreneurs is warring over the tides, the next big thing in alternative power. As oil and natural gas prices climb, upstarts such as Verdant and rival Oceana Energy Co. are vying for investors' money and staking claims to America's coastal waterways.

Since 2005, the U.S. Federal Energy Regulatory Commission, which regulates the energy industry, has granted Oceana, Verdant and six other companies the exclusive right to study the tides in 22 locations, from the East River in New York to the Icy Passage in Alaska. If the companies can figure out how to make projects pay there, they'll get first dibs on federal licenses. The price of one of these potential golden tickets: $0.

The froth is flying. Washington-based Oceana has angered Verdant Power executives by seeking a site just north of Verdant's East River turbine farm.

Oceana, chaired by William Nitze, son of the late NATO architect Paul Nitze, has also irked the city of San Francisco by laying claim to the currents that swirl beneath the Golden Gate Bridge.

The company has applied for a total of 13 study permits and is trying to use its pull in Washington to steer taxpayer money its way.

"They're claim jumpers," Verdant Power co-founder William "Trey" Taylor says of his competitor.

Oceana co-founder John Topping says his company has played by the rules. He says the best tidal sites were there for the taking.

"Somebody is going to do it, and we want to be the somebody," says Topping, president of the Washington-based Climate Institute, which promotes awareness of global warming.

The idea that the oceans might yield an endless supply of pollution-free power has lured an odd cast of characters. Tudor Jones joins a crush of engineers, lawyers and former politicians racing to master the tides.

One of Oceana's consultants helped design a bunker-busting nuclear bomb for the U.S. military. An engineer at Dublin-based tide power company OpenHydro Group Ltd. used to advise Ferrari SpA.

Another tide entrepreneur built a fast boat for Colombian drug smugglers, which landed him in prison.

Venture capitalists have invested millions of dollars in solar-energy and geothermal startups.

Money managers such as Tudor Jones are clamoring after companies that cook up gasoline substitutes from corn, sugar and soybeans. Alternative energy stocks have surged the way dot-com shares did in 1999. The 43- stock WilderHill Clean Energy Index has rocketed since its August 2004 debut, rising 66 percent as of May 7.