After a poorly-received release in the U.S. as "Something Waits In The Dark", New World Pictures re-released it as "Screamers", with a completely new (and mis-leading) marketing campaign promising "You will actually see someone turned inside out... while he's still alive!", with a newly-filmed trailer featuring just that. Though this scene was not in the actual film, New World were forced to splice the actual footage from the trailer into all existing theatrical prints, after riots occurred by angry drive-in customers who were mis-lead. Since the footage was never inserted into the film's negative print, the video version does not contain this scene.
The out of print British video was trimmed for time reasons. Simply, the video company Vipco video cut the 99 minute film to fit on a 90 minute tape. Unlike their release of the Driller Killer which removed a 6 minute chunk for the same reasons, the cuts to Island of the Mutations are spread throughout the film- making it hard to work out exactly what's missing. However the tape is noticeably absent of Jose discovering the underground ship and being knocked out by Rackham's henchmen and Claude being beaten up, force-fed a Voodoo potion and suffering a nightmare.
The German TV version removes around 10 minutes of footage after the boat is sank by the fishmen. This robs the film of its introduction to the main characters, and now begins with a fishman killing one of the boat's crew (in the complete version he's looking for food to help the other survivors). The German print is also missing the following scene where the other members of the crew find his body, in order to belatedly introduce them in the scene after.