A huge swarm hundreds of kilometers across and comprised of tens of millions of jellyfish arrived in Israel this week causing woe for Israeli beachgoers and greater troubles for the electric company.

Jellyfish regularly arrive en masse, referred to as blooms. Two years ago, University of Haifa researchers completed a study of jellyfish off the coast of Israel, concluding that the blooms, usually occurring during the summer months, are drawn to the warmer waters, 83 degrees Fahrenheit and higher, and arrive in conjunction with a full moon.

The jellyfish are Galil Rhopilema nomadica, otherwise known as nomad jellyfish which are indigenous to the Indian Ocean. The nomad jellyfish is light blue and the bell is rounded. It can grow up to 22 pounds, and its bell is commonly 15-35 inches in diameter. Scientists first observed the species off the coast of Israel in 1976 and believe the species travels to Israel via the Suez Canal that connects the Mediterranean with the Red Sea.

The swarms of jellyfish are a nuisance to bathers. Their sting is painful but there have been no known deaths attributed to being stung by a jellyfish. Websites have been set up to help beachgoers avoid problem areas. The jellyfish are currently focused on Ashdod and Ashkelon in southern Israel with scattered sightings off Haifa and Tel Aviv.

The phenomenon has proven to be more problematic for electricity and desalination plants. For the past month, the plants have been coping with jellyfish clogging the filtering systems and stopping the flow of seawater, used for cooling in the power plants and to produce fresh water in the desalination plants.