Recently, engineers and marine biologists at the University of California have developed an eel-like robot which can swim silently in salt water without the use of an electric motor. Instead, the robot uses artificial muscles that fill with water to propel itself. The foot-long robot, which is connected to an electronics board that remains on the surface of the water, is also virtually transparent.
https://www.sciencedaily.com/releases/2018/04/180426102906.htm
This article relates to engineering since robotic engineers and marine biologists have applied their knowledge to create something better than things previously made.
