Swimmers wanting to avoid being stung by jellyfish may want to watch the sky as much as the sea after Israeli researchers found a link between their arrival and the phase of the moon.

The Israeli study found the lunar calendar is a key determinant of when jellyfish arrive on the Mediterranean country's shores.

In the middle of the lunar months -- the days before and during the full moon -- jellyfish are far more likely to swarm the beach, potentially stinging humans, the research found.

"We were surprised by our findings," researcher Avi Algazi told AFP. "We knew the moon has a big influence on a lot of things but we didn't so far have statistical data on the correlation between jellyfish and the moon."

The research was conducted by the Israel Electric Corporation in conjunction with the University of Haifa in northern Israel.

The jellyfish are a threat to Israel's power supply as they get sucked into the country's main power station, which uses sea water for cooling.

The researchers looked at when the power station was most badly affected by the jellyfish and correlated it with the moon and water temperatures.

In total, 94 percent of jellyfish swarms arrived after the middle of the year when the seas are warmer and during the second and third weeks of the lunar month.

The ideal water temperature for the jellyfish is between 28.2 and 30 degrees, the research found.

Algazi stressed the research so far only applied to local conditions but said he hoped "the results could be checked in other parts of the world."