Caught last night by my motion camera. Reminds me of the undulating fins along the siders of cuttlefish. I think I know what it was, but I'll allow you to speculate...

http://vftp.net/virtual1/temp/MFIF/flyby.mov

cuttlefish:

http://www.youtube.com/watch?v=5qwt_BM7wec

I work for the Department of Redundancy Department