To scientists, it represents a tantalizing possibility: a new, plentiful and uninterrupted source of clean energy.
Florida Atlantic University researchers say the current could someday be used to drive thousands of underwater turbines, produce as much energy as perhaps 10 nuclear plants and supply one-third of Florida's electricity. A small test turbine is expected to be installed within months.
"We can produce power 24/7," said Frederick Driscoll, director of the university's Center of Excellence in Ocean Energy Technology. Using a $5 million research grant from the state, the university is working to develop the technology in hopes that big energy and engineering companies will eventually build huge underwater arrays of turbines.
From Oregon to Maine, Europe to Australia and beyond, researchers are looking to the sea currents, tides and waves for its infinite energy. So far, there are no commercial-scale projects in the U.S. delivering electricity to the grid.
Because the technology is still taking shape, it is too soon to say how much it might cost. But researchers hope to make it as cost-effective as fossil fuels. While the initial investment may be higher, the currents that drive the machinery are free.
There are still many unknowns and risks. One fear is the "Cuisinart effect": The spinning underwater blades could chop up fish and other creatures.
Researchers said the underwater turbines would pose little risk to passing ships. The equipment would be moored to the ocean floor, with the tops of the blades spinning 30 to 40 feet below the surface, because that's where the Gulf Stream flows fastest. But standard navigation equipment on ocean vessels could easily guide them around the turbine fields if their hulls reached that deep, researchers said.
And unlike offshore wind turbines, which have run into opposition from environmentalists worried that the technology would spoil the ocean view, the machinery would be invisible from the surface, with only a few buoys marking the fields.
David White of the Ocean Conservancy said much of the technology is largely untested in the outdoors, so it is too soon to say what the environmental effects might be.
"We understand that there are environmental trade-offs, and we need to start looking to alternative energy and everything should be on the table," he said. "But what are the environmental consequences? We just don't know that yet."
The Federal Energy Regulatory Commission has issued 47 preliminary permits for ocean, wave and tidal energy projects, said spokeswoman Celeste Miller. Most such permits grant rights just to study an area's energy-producing potential, not to build anything.
The field has been dealt some setbacks. An ocean test last year ended in disaster when its $2 million buoy off Oregon's coast sank to the sea floor. Similarly, a small test project using turbines powered by tidal currents in New York City's East River ran into trouble last year after turbine blades broke.
The Gulf Stream is about 30 miles wide and shifts only slightly in its course, passing closer to Florida than to any other major land mass. "It's the best location in the world to harness ocean current power," Driscoll said.
Researchers on the West Coast, where the currents are not as powerful, are looking instead to waves to generate power.
Canada-based Finavera Renewables has received a FERC license to test a wave energy project in Washington state. It will eventually include four buoys in a bay and generate enough power for up to 700 homes. The 35-ton buoys rise above the water about 6 feet and extend some 60 feet down. Inside each buoy, a piston rises and falls with the waves.
The company hopes later to be the first in the U.S. to operate a commercial-scale "wave farm," situated off Northern California. The project with Pacific Gas and Electric calls for Finavera to produce enough electricity to power up to 600 homes by 2012. Finavera eventually wants to supply 30,000 households.
Roger Bedard of the Electric Power Research Institute said an analysis by his organization found that wave- and tide-generated energy could supply only about 6.5 percent of today's electricity needs.
Finavera spokesman Myke Clark acknowledged that wave energy is "definitely not the only answer" to the nation's power needs and is never going to be as cheap as coal. But it could be "part of the energy mix," and could be used to great advantage off the coasts of Third World countries, where entire towns have no connection to electrical grids, he said.
Nick Furman, executive director of the Oregon Dungeness Crab Commission, said he fears the wave technology could crowd out his industry, which last year brought in 50 million pounds of crab and contributed $150 million to the state's economy.
"We've got a limited amount of flat sandy bottom on the Oregon Coast where we can put out pots and where we can fish, and the wave energy folks are telling us they need the same flat, sandy bottom," Furman said.
"It's not the 10-buoy wave park that has the industry concerned. It's that if it's successful, then that park turns into a 200- or 400-buoy park and it just keeps growing."