The human body does many things well, but swimming isn't one of them. We're embarrassingly inefficient in the water, able to convert just 3 or 4 percent of our energy into forward motion. (Even with swim fins, we're only 10 to 15 percent more efficient.) But a new, dolphin-inspired fin promises to fuel the biggest change in human-powered swimming in decades, putting beyond-Olympian speeds within reach of just about anyone.



Culminating decades of research, engineer and inventor Ted Ciamillo, an inventor and engineer in Athens, Ga., who made his name (and fortune) building high-performance bicycle brakes, created what he has dubbed the Lunocet, a 2.5-pound (1.1-kilogram) monofin made of carbon fiber and fiberglass that attaches to an aluminum foot plate at a precise 30-degree angle. With almost three times the surface area of conventional swim fins, the semiflexible Lunocet provides plenty of propulsion. The key to the 42-inch- (one-meter-) wide fin's speed: its shape and angle, both of which are modeled with scientific precision on a dolphin's tail.



These sprinters of the sea can swim up to 33 miles (53 kilometers) per hour and turn up to 80 percent of their energy into thrust.



"The mechanism functions like a wing to generate a lift force," which is directed forward and turned into thrust, says Frank Fish, a marine biologist at West Chester University of Pennsylvania. "This propulsive mechanism is extremely efficient compared to conventional rigid marine propellers." Fish, a specialist in the swimming morphology of marine mammals, provided Ciamillo with data from CAT scans of dolphins' tails that he used to design his fins, which went on the market last year for $1,800 each.



Lunocet users have already hit about eight miles (13 kilometers) per hour, nearly twice as fast as Olympic Gold Medal swimmer Michael Phelps at his speediest.



Using the Lunocet, some swimmers are close to being able to breach completely out of the water, like whales. Ciamillo envisions a new high-speed, free-diving community of swimmers united around "hydrotouring": long-distance swimming expeditions using Lunocets to cover dozens of miles a day, with participants carrying streamlined, waterproof packs containing only a global positioning system (GPS), satellite phone, and enough food and water for a few nights on shore.



The fin could also have a "profound effect" on the sport of free diving (where divers compete to see who can go the deepest while holding their breath), says Grant Graves, president of the U.S. Apnea Association, the country's leading competitive free diving organization. Its efficiency could let those who dive by holding their breath set depth records by going deeper more quickly. Still, speed isn't everything underwater. "The faster you go, the harder you have to work," since drag increases as the square of velocity, he says. "There's a sweet spot between friction, speed, oxygen consumption and distance."



Another attempt to balance that equation is taking shape in the labs of inventor and entrepreneur Dean Kamen's company, DEKA Research and Development Corp. in Manchester, N.H. The creators of the Segway two-wheel, one-person electric vehicle are working with the Defense Sciences Office of the U.S. military's Defense Advanced Research Projects Agency (DARPA), the research arm of the U.S. Defense Department, to develop the PowerSwim, a high-efficiency, human-powered propulsion system for combat and reconnaissance swimmers. A fiberglass spar (pole) clamped between the calves holds two oscillating foils of carbon fiber, a wide one at the hips and a narrower one at the feet. A shallow squatting motion makes the foils undulate, creating vortices that push forward against the trailing edge and provide thrust.



This design uses the largest leg muscles instead of just the calves and ankles, says DARPA Defense Sciences PowerSwim Program Manager Lt. Col. John Lowell. Top speed is about 2.5 miles (four kilometers) per hour, which still works with scuba gear, but more important, the PowerSwim is 70 to 75 percent efficient at translating effort into propulsion. "We're getting to the point where its getting harder to imagine getting much better than that," Lowell says. DARPA hopes to have working prototypes ready for military divers to test by the end of the year.



Ciamillo is also planning a demo the Lunocet for the Marine Corps's amphibious unit, and is continually refining the fin's pitch control mechanism, which dictates the angle between fin and feet, in an attempt to improve efficiency and speed. He notes that he won't be patenting the Lunocet's design. "If you're taking ideas from nature," he says, "how can you then go to the patent office and say these are mine?"