It looks like a jellyfish. It swims like a jellyfish. But, the tentacled artificial creature above, dubbed the "Medusoid," is actually created by scientists at Caltech and Harvard with rat cells:
Nick Collins of The Telegraph has the story: Link
It is able to mimic the swimming movement of a jellyfish thanks to muscle cells from rat hearts which were implanted onto its silicon frame and grown into a pattern similar to the muscles of a real jellyfish.
By applying an electric current to a container of conducting liquid, the scientists demonstrated they could "shock" the muscles into contracting so that it began to move through the water.