Their arrival on the Irish coast has come weeks ahead of normal.
Bantry Bay is just one part of the West Cork coastline that has had an early and unwelcome invasion of Lion's Mane jellyfish, which are considered dangerous and can give bad stings. There is also risk that some people who are stung may suffer anaphylactic shock.
According to experts their arrival on the Irish coast has come weeks ahead of normal, as the sea is warmer due to the current heatwave. John Leech, chief executive of Irish Water Safety, said that the number of jellyfish was on the rise because there were not enough predators due to plastic pollution.