The sometimes mentioned Sea Spider "system" was simply a complex and unsuccessful experiment with a very large suspended array in the Pacific. It was part of LRAPP as noted on page 181 of the reference. The experiment was part of the Pacific Acoustic Research Kaneohe — Alaska (PARKA) II experiment in 1969. Parts of Sea Spider ended up off Bermuda, designated Testbed for more experiments. That array was installed by unusual cable and installation vessel Naubuc but also failed (See Naubuc).
The web page A Century of Service: The U.S. Navy on Cape Henlopen has a detailed description with photos and illustrations of this NAVFAC and the cable and array locations. The original phonetic name for the system was GEORGE. The photo of a cross section of the old 21 quad cable is of particular interest.
"Ongoing Research at ARL:UT". Arlut.utexas.edu. University of Texas at Austin Applied Research Laboratories. Archived from the original on 2013-06-19. Retrieved 2013-12-13.
"Ongoing Research at ARL:UT". Arlut.utexas.edu. University of Texas at Austin Applied Research Laboratories. Archived from the original on 2013-06-19. Retrieved 2013-12-13.