The Indian Ocean record attempt by rowers James Ketchell and Ashley Wilson has been delayed due to unpredictable weather conditions.
Adventurer James and Scout leader Ashley, who survived Hodgkin lymphoma at the age of 19 and has lived with epilepsy from the age of seven, were due to begin their attempt to cross the 3,600 miles from Australia to Mauritius on May 8.
But concerns were raised that their feat to beat the fastest recorded time of 85 days, two hours and five minutes would be threatened by severe weather conditions caused by Cyclone Quang.
Ashley, 37, from Wickham, Hampshire, said: "The news from the challenge weather router Charlie has come as a great blow to both James and myself.
"Having meticulously planned our departure for this weekend, this latest severe weather update may stall our launch from Geraldton by several days.
"It just goes to show you who's the real boss in this challenge and we have to respect both the ocean and its weather system to get to Mauritius safely."
Last year James, 33, from Basingstoke, became the only person in history to row the Atlantic Ocean, climb Everest and cycle unaided around the world.
He added: "This last-minute delay is necessary to avoid any potential Cyclone Quang-type weather in the coming days that could have proved catastrophic to the challenge and our world record attempt."
The departure delay does mean that the two Scout ambassadors will have the opportunity to visit scouting and young people groups in Western Australia as they continue to raise awareness and money for Young Epilepsy, The Scout Association and The Elifar Foundation.
Lisa Farmer, director of development at Young Epilepsy, previously said:
"Everyone at Young Epilepsy is amazed by Ashley and James's courage, and very moved that they are taking on this challenge to help inspire young people with epilepsy.
"Ashley is a hero and we know that thousands of young people will be glued to this adventure. He is an inspiration and is helping us by raising vital funds and fighting stigma."
A new departure date has been set for either May 16 or May 17 from Geraldton marina. To follow their progress or support their fundraising efforts, visit www.nothings-impossible.co.uk.