A biomimetic robotic fish created by Yahya Modarres-Sadeghi at the University of Massachusetts in Amherst and colleagues can accelerate a speeds of up to 4 gs.
(Very quick robotic fish)
A startled pike can accelerate at about 15 g for a tenth of a second. A robot with that kind of acceleration could be well suited to covert operations or navigating turbulent water.
The team built a 50-centimetre-long rubber fish modelled on a member of the pike family called the chain pickerel. Running lengthwise inside was a metal strip bent into a C-shape and kept that way by a clamping mechanism. When released by an external pneumatic actuator, the potential energy of the bent strip is converted into kinetic energy, causing the model's tail to whip one way and then the other.
Under water this resulted in an acceleration of just over 4 g, eight times that achieved by previous robotic fish.
In his 2002 story Slow Life, science fiction author Michael Swanwick writes about robot fish who help explore distant worlds:
Consuelo carefully cleaned both of her suit’s gloves in the sea, then seized the shrink-wrap’s zip tab and yanked. The plastic parted. Awkwardly, she straddled the fish, lifted it by the two side-handles, and walked it into the dark slush.
She set the fish down. "Now I’m turning it on."
The Mitsubishi turbot wriggled, as if alive. With one fluid motion, it surged forward, plunged, and was gone.
(Read more about the robot turbot)