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.
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).
There are actually eight actors playing eight different zombies in the film, although it appears that there are many more.
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.
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.