What do you call a grouping of jellyfish? Residents in the northern Italian port town of Trieste found out on Wednesday when a 'smack' of jellyfish swooshed into the harbour.

Local residents took to social media to show their array of video and pictures of the grouping which experts say was the 'rhizostoma pulmo' jellyfish, one of the biggest to be found in the Mediterranean Sea.

Environment groups said the unusual gathering was probably down to particular winds and currents that had pushed the jellyfish into the harbour.

They remained on top of the water where the temperatures were warmer and where they would find more plankton.