PowerSwim

The PowerSwim is a device somewhat like two pairs of long thin airplane wings which are fastened to a scuba diver's hips and legs: the longer pair (about convert|6|ft|m wide or a bit less) at the hips and the shorter pair at the ankles. It was developed by DARPA. It is claimed to let a scuba diver or frogman swim much faster (250%) than with swimfins for the same amount of bodily effort, if used correctly, and being not motorized, it makes no motor noise to be heard by hostile hydrophones. It works somewhat like a penguin's or plesiosaur's side-mounted flippers. Its estimated cost is less than $500. The diver uses it by moving his legs up and down together like with a monofin. It is claimed that the length of the front wing lets it operate outside the cone of wake that starts at the diver's shoulders.

Likely disadvantages:
*The width of the device would make it difficult to go through narrow gaps or near alongside something.
*It ties the diver's feet together.

External links

*http://www.origin.popularmechanics.com/technology/military_law/4223354.html Image and description
*http://www.darpa.mil/dso/thrusts/bio/biologically/powerswim/index.htm
*http://gizmodo.com/gadgets/military/darpas-powerswim-brings-out-the-aquaman-in-you-318195.php Images and description
*http://www.slate.com/id/2171923/entry/2171925/