Reading the account below of the Alaska Ranger crew at pre-dawn on 3/23/2008, it seems that strobes were key.

The crew got off a distress message with their lat/lon before sinking, and when the USCG helo got there:

" ...there it was—a light. Then two, three ... five. The crew saw what looked like a poorly lit runway, a string of strobes flashing on and off over almost a mile-long stretch of ocean."

http://www.popularmechanics.com/technology/aviation/crashes/4267469