The fearless 41-year-old, who swam a record 197km through shark-infested waters from Mexico to Cuba in 1998, has revealed she has a malignant melanoma on her back.
Speaking to New Idea, Susie is praying a looming operation, which will make a nine-centimetre long incision, will be enough to stop the cancer from spreading.
The mother of Paris, 7, ,Capri, 5, and River, 3, says she started crying when she heard the news from her doctor, but is drawing on the strength that took her to the top of the endurance swimming world in the 1990s.
Susie says her story is also a warning to others to be safer in the harsh Australian sun.
She admits that she never used sunscreen while competing in her many gruelling endurance tests, which also included a Jamaica to Cuba crossing and the fastest ever two-way English Channel swim.
Susie admits it was only a fluke that alerted her to her skin cancer.
Susie was prompted to visit her doctor after a stranger noticed a mole on her back and warned her of its potential danger.
“Hopefully, they will get all the melanoma out,” she says.
“If they don’t, I will have to have further tests and scans to see if it has spread anywhere else in my body.”
Susie is also drawing strength from the support of her new parter, Perry Cross, 40, who became a paraplegic at just 19 after being tackled in a rugby game.
“He supports me through everything, and this is no different,” adds Susie, who met Perry at a charity dinner in 2014.
“We’ve been talking about our future together. This is just a little hurdle we have to get past first.”
For more tips on how to stay sun safe and spot a potential skin cancer, click here.