A combination of strong currents, severe winds and the weak propulsion system of the jellyfish makes these creatures susceptible to washing ashore. According to ReefEd, a service of the Great Barrier Reef Marine Park Authority, jellyfish have only a weak internal pumping mechanism that allows them to float, but they cannot steer away from danger. When jellyfish are caught in a strong current, they have no means of escape.
Strong weather systems like hurricanes and regular events like the full moon both affect jellyfish. The pull of the full moon exacerbates strong currents, making jellyfish more likely to wash ashore. A small number of jellyfish are pushed ashore by the regular changing of the tides, but deposits of hundreds of jellyfish are the result of unusual tidal activity.
However, washing ashore is part of the natural life cycle of jellyfish, says Matt Babineau of the North Carolina Aquarium at Fort Fisher. Jellyfish are 98 percent water. When they wash up on shore, jellyfish quickly dry out and die. However, Babineau advises against picking up jellyfish or throwing them back into the ocean. Some jellyfish are harmless, but others have powerful, painful deadly stings. Additionally, the jellyfish cannot fight against the tidal conditions that washed them ashore, so any jellyfish thrown back into the ocean are likely to wash ashore again.