Battery-free Robotic Fish: Swimming with Robot Blood

Robotic fish is powered by \”Robot-Blood\” and has no battery
This robot fish is about 40 centimeters in length and made from a rubbery, soft material.

The fluid is circulated in a similar way to blood, and the fish’s body is propelled.

Source:
https://interestingengineering.com/innovation/robotic-fish-is-now-powered-by-robot-blood-for-greater-autonomy