The "Blue Light" was only witnessed in writing by a crew member of the Housatonic...the Confederates reported in writing that the appropriate signal was seen and no discription of what that was given. The "Blue Light" could have been from another surface vessel. From discussions with people on this board that tested the "Blue Light" used normally during this time period, a burning flare, it would have required the user to hold a hot burning torch or sorts above his head, in pitching waves, from the hatch of the Hunley...not very safe.