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Jellyfish swim at Palm Island's Atlantic resort in Dubai.
Diana Nyad says it may be impossible for her to ever complete a swim between Cuba and the Florida coast. The Southern California swimmer failed in her fourth attempt to swim across the Gulf of Mexico.
She battled stormy waters and extreme exhaustion, but it may have been something much smaller that posed the biggest challenge: jellyfish.
Nyad suffered several jellyfish stings during her time in the water. She also said that she's never seen so many jellyfish in these waters before.
Many biologists have been watching global jellyfish populations to see if there really has been an explosion. The National Science Foundation published a report in 2008, Jellyfish Gone Wild, that examined potential reasons for the explosion of jellyfish population. Climate change has led to changes in aquatic habitats and increased population of jellyfish prey, leading to higher populations. Also, over-fishing of traditional jellyfish predators has led to an increase of jellyfish.
Monty Graham, professor at the University of Southern Mississippi