The original negative mysteriously disappeared over 20 years ago. The print used for the Blue-Underground DVD is from director Ken Wiederhorn's personal collection.
There are actually eight actors playing eight different zombies in the film, although it appears that there are many more.
Headlining stars John Carradine and Peter Cushing each worked five days. Carradine earned $5,000 while Cushing earned $25,000 (plus first class airfare to and from London, hotel accommodations and a driver).
The wreck of the Nazi freighter where the zombies reside is the SS Sapona, a concrete-hulled cargo steamer that ran aground near Bimini in the western Bahamas during a hurricane in 1926.
Jay Maeder, who plays one of the zombies, is actually a reporter for the Miami Herald. He wrote a article in the August 10, 1975 Sunday Miami Herald about his experience acting the part of a Nazi zombie for the Shock Waves movie. The article was titled "I was a Zombie". During filming, he never told anyone involved with the movie that he was a reporter.