The International Swimming Federation (FINA) Marathon Swim World Series is due to continue tomorrow, with 41 athletes from five continents descending on Lac St-Jean in Quebec.
Tomorrow's race is the fifth of eight events on the 2018 calendar, with Lac St-Jean featuring on the circuit every year since its inception in 2007.
Andreas Waschburger, the 31-year-old from Germany, could jump from fifth place to first in the men's event if he wins tomorrow.
Allan do Carmo from Brazil, meanwhile, will want to gain podium points having finished fourth in Quebec last year.
On the women's side another Brazilian in Ana Marcela Cunha is the favourite tomorrow.
The 26-year-old 10-time World Championship medallist and two-time Olympian has already won more World Series races than any woman in history.
If she wins tomorrow it will mark her 20th victory on the circuit, but her compatriot, 22-year-old Viviane Jungblut, will be among those trying to stop her.
She finished third in Quebec last year in her first season since leaving the swimming pool.
The men’s race is due to begin at 11.45am local time, followed by the women's race at 2.45pm.
In order to earn points, swimmers must complete a 1.67-kilometres loop six times.
Last year, the top five men finished in just under two hours, while the fastest woman hit the timing pad in two hours and three minutes.