As well as the sharks, 29-year-old Chloe McCardel will battle exposure, swift sea currents, stinging jellyfish and extreme fatigue as she attempts the record swim from Cuba to Florida this week.
The 103-mile (166km) journey is considered the ‘holy grail’ of marathon swimming, with numerous failed attempts having been made at the treacherous crossing.
McCardel, who is a veteran swimmer of the English Channel and other endurance swims, believes she has the strength and the determination for the dangerous crossing.
“At the moment it’s the most high-profile marathon long-distance swim, and swimmers really want to come here and be the first,” she said in Havana, Cuba.
“It’s very important; it’s like winning a gold medal.”