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?"