America's underwater special forces ops might not like it at first, but this dolphinlike device, PowerSwim, will let them reach targets fast -- and without having to catch their breath. The device is compatible with standard scuba gear, as well as the front-mounted rebreathers (artist sketch, above) used by special operations personnel to avoid telltale bubble trails.
Humans are terrible swimmers, converting roughly 3 percent of their kicks, strokes and general underwater exertions into forward motion. We can boost our efficiency to 10 percent by adding fins, but dolphins, by comparison, can turn 80 percent of their energy into thrust. Not to be outdone, the Pentagon's research wing, DARPA, is developing a contraption that lets Navy SEALs and other combat divers swim faster, and with less effort.
Instead of kicking, PowerSwim calls for a kind of undulation as its hinged foils pivot up and down. Similar to the way a dolphin or tortoise pumps its fins, this motion generates both lift and thrust. And while artificial fins operate within the swimmer's own wake (they form a kind of expanding cone, starting at a swimmer's shoulders), the PowerSwim's lead foil -- or propulsor foil -- sweeps through the water just outside that wake.
See how the PowerSwim works at Military.com.