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
Skin Deep (webcomic) often works to establish a theme of different versions of normalcy, promoting acceptance and diversity. The story of Skin Deep chronicles around a world where most, if not all, mythical creatures, objects and terminology (e.g magic) exist, but are hidden away from the world of humans. Most Mythical Creatures have magical medallions, which can hide their true forms from human sight. The comic is split into chapters, some of which are single multi-page short stories, others are multi-chaptered long stories. The story, as of February 2018, mostly takes place in the year 2004, though one story takes place in the