Why is the Viper Shark frequently nicknamed the alien shark?

Answer

Because of its metallic, otherworldly appearance when its jaw is open

The nickname alien shark arises from the creature's startling and somewhat unsettling appearance. Specifically, when the shark opens its mouth to reveal its interlocking, serrated, blade-like teeth, the display appears metallic and reminiscent of science fiction depictions, which led to the popular designation.

Why is the Viper Shark frequently nicknamed the alien shark?
animalevolutionmarinesharkdogfish