RoboFish
Yes, they’re real.
Actual autonomous robots that mimic fish are no longer just science-fiction. According to this article on the BBC, the London Aquarium not only has them, but has them swimming in a tank with actual fish. Primarily as a marketing gimmick at the moment, but, still, they’re in there just acting like fish. Currently, they’re trying to get them to “feed” like biological animals, too, but, at the moment, they’re on batteries that last rough 5 hours.
Obviously, these little blighters are part of a scientific experiment to see how the fish and robots interact, as well as representing a step in the ever popular quest for artificial life. Any way you slice it, robofish are pretty interesting.