A new study of 60 beaches in Southern California shows water pollution varies with the lunar cycle, reaching the highest levels when tides are ebbing during the New and Full Moon.

These findings could change the way beach managers evaluate swimming safety.

Study leader Alexandra Boehm of Stanford University, says it is riskier to swim during spring-ebb tides compared to all other tidal conditions.

Levels of the bacteria enterococci are twice as likely to be above accepted limits during spring tides, which occur during Full or New Moon.

Spring tides are given their name because they "spring up" in relation to normal high tides; they have nothing to do with the season.

The Moon is chiefly responsible for Earth's tides, with the Sun contributing a little as well.