Fish scale the surface, interacting only with the riblet tips, not causing any high-veloctiy flow in the valleys. Since this high velocity flow now only interacts with the riblet-tip, which is a very small surface area, the momentum transfer which causes drag is now much lower than before, thereby effectively reducing drag. Also, this reduces the cross-stream velocity fluctuations, which aids in momentum transfer too. The rough, sandpaper-like texture of shark and ray skin, coupled with its toughness, has led it to be valued as a source of rawhide leather, called shagreen. One of the many historical applications of shark shagreen was
Terror-Creatures from the Grave Several home video releases of the film have many different versions of the film. The DVD from Something Weird Video has a running time of 77 minutes and 30 seconds, and includes a nude scene with Mirella Maravidi. This scene is not included in Sinister Cinema's video release, which is four minutes longer due to an extra dialogue scene. Severin Films has announced a planned Blu-ray disc release of the film. In a contemporary review, the "Monthly Film Bulletin" was disappointed that the "creatures" of the film's title are "confined to the occasional intrusion of a plague-ridden hand or arm",