An unusual kind of breed has been introduced to visitors at the London Aquarium - a robofish!
They sense nearby objects and swim in a different direction
The fish-bot is based on a common carp, and will swim around a specially designed tank, dodging past objects guided by special sensors on its body.
Cyber-fish have been in development for 10 years, but creators say the latest model is the best ever.
Experts hope one day the robots will be used for searching the seabed, detecting oil leaks or even spying.
The fish are about 50cm long, 15cm high and 12cm wide and are covered in light-reflective scales to look as realistic as possible.
Designers say it has the acceleration of a pike and the navigation skills of an eel. It is covered in tiny sensors which warn the machine when it is swimming too close to something.
It can swim at a maximum speed of 50cm a second, but can be slowed down to preserve battery power if need be.
Real fish companions
The three robots will live in the tank with real fish and will be on display in the London Aquarium.
In July 2003 a shark model called Roboshark 2 was put into a tank with fish at the National Marine Aquarium in Plymouth.