When Ceinwen Roberts and Rohan Hollick tell people they plan to swim the Rottnest crossing three times in succession this weekend, most think they're crazy.
The pair want to become the first people to make the triple crossing, with only a short break at each beach, in an event called Swimming To Freedom For Walk Free to raise awareness of the Walk Free movement against modern slavery.
Neither is a stranger to long-distance swims.
Ms Roberts, 32, is a veteran of the English Channel crossing and hopes to complete the Manhattan Island Marathon Swim in June. Mr Hollick, 42, has already completed two double Rottnest crossings.
But at 59.1km, a triple crossing is further than both the English Channel and the Cook Strait between the North and South Islands of New Zealand.
Ms Roberts and Mr Hollick plan to start the marathon under the stars, leaving Rottnest at midnight and hope to arrive at Cottesloe beach by 6am, be back at Rottnest for midday and finish at Cottesloe at 6pm.
Ms Roberts admitted being scared of swimming in the dark but said she wanted to turn her fear around and make it fun and exciting.
"It is a crazy thing to do, I understand that, but you only live once - so why not do crazy things," she said. The final date of the swim will be determined by the weather but they are planning to make the crossings on Saturday to coincide with the final day of Sculpture by the Sea at Cottesloe.
Mining magnate Andrew Forrest, who established Walk Free with his wife Nicola in May last year, has offered to paddle the midnight crossing.
Mr Hollick said though there were risks involved, such as the threat of sharks or hypothermia, they did not compare with the dangers faced every day by people in slavery.