Future director--then head of publicity and marketing for New World Pictures-- Jim Wynorski is the one who came up with the title change and tagline, and did additional filming, in order for this to be known as "Screamers" in the US.
For the US version, distributed by Roger Corman's New World Pictures, Corman had approximately 15 minutes of new footage shot, of which 12 minutes was for the opening.
A sequel by the same director, Sergio Martino was released about 16 years later, titled La regina degli uomini pesce (1995) ["The Fishmen and Their Queen"].
Mel Ferrer, Jim Alquist, Eunice Bolt, Tom J. Delaney and Cameron Mitchell only appear in the US version.
Set in 1891.