A robot designed like a jellyfish has been built by scientists in America.
It's called Robojelly and could be used for underwater rescue operations.
It moves in water by copying a jellyfish's natural swimming movement and is powered by a chemical that's already in water called hydrogen.
It's in early stages of development but because it will be fuelled by hydrogen, it doesn't need batteries and could in theory keep going forever.
The research has been carried out by the US Office of Naval Research which looks into projects like Robojelly that might benefit the US Navy in the future.