A group of explorers in South America will wear condoms to stop fish swimming up their penises.
The New Zealand team plan to swim in the Amazon and don't want the small catfish in their bladders.
The fish is attracted to urine and has to be surgically removed from the bladder, where it dies.
Expedition doctor Marc Shaw says: "It's the only place in the world where you put on a condom to go swimming."
Dr Shaw, from Hamilton's Anglesea Clinic, says the explorers could wear a cricket box instead.
He adds their third option is to "just hold tight."
"If the fish swims up there the pain is excruciating and the fish has to be surgically removed from the bladder," he says.
The group of 26 plan to study people's use of water and will end their trip in Venezuela, the Waikato Times reports.
