There is a guy on Craig's list trying to sell a Mirage Drive with turbo fins. He obviously does not know how the thing works because in the text he describes it as "ready to bolt on to your kayak"?
My guess is this guy found or stole the drive. If anyone lost one, check out this link.
http://sandiego.craigslist.org/csd/boa/1672250291.html
Bob