A team of marine biologists claimed they witnessed dolphins swim under a jellyfish and, with a quick flick of its tail, shoot it out of the water.
The bottlenose dolphins, which were off the Welsh coastline at the time, were caught on video for the first time playing jellyfish football.
And one dolphin is seen flipping the jellyfish 6ft in the air.
Scientists suggested their game could go some way to explaining why dolphins in captivity are so skilful with balls in sealife parks around the world.
Jonathan Easter, 23, who saw the dolphins at play, said: "One thing is for sure, they were having fun.
"There were floating blobs of jelly and the dolphins were flipping them about.
"They swim under the jellyfish, then at the right moment flick their tail up to give it a good 'kick'.
"They were not always accurate but when they had a direct hit the jellyfish were literally kicked out of the water.
"We have been studying individual dolphins in Welsh waters for some time but we got more than we expected from this trip.
"These incredible images provide a privileged insight into the lives and behaviour of bottlenose dolphins.
"But this behaviour has never been seen before and it presents more questions than answers!"
Some of the Barrel jellyfish reportedly died from being flipped.
Marine biologists from the Countryside Council for Wales, Sea Watch Foundation and Marine Awareness North Wales were studying bottlenose dolphins in Cardigan Bay, off the welsh coast.
The area has Britain's largest coastal population of bottlenose dolphins.
Every summer, between 150 and 250 dolphins inhabit the waters, which form significant breeding and feeding grounds.