Zsofia Balazs once saw a fish eat another fish while she swam an open-water race.
"That kind of freaked me out," she says.
Richard Weinberger spent much of a river race in Mexico wondering where the crocodiles were lurking.
Canada's two marathon swimmers at the Summer Olympics in London both admit their sport's wild environments can make them feel uneasy.
In the pool, it's man against man in a controlled setting. In open-water swimming, it's man against man and nature.
No pristine water with black lines clearly visible below for Balazs and Weinberger.
Open-water racing is in oceans, rivers, lakes and ponds, where creatures, as well as swimmers, are in competition with each other.
"Just don't look down and think about what's below you," is the advice of Balazs.
Balazs, from Toronto, and Victoria's Weinberger have raced in water so murky they couldn't see their hands in front of their faces.
While that may have kept Weinberger from witnessing any "Wild Kingdom" moments, the 22-year-old isn't sure ignorance is bliss. Sometimes imagination is worse.
"If I see anything I'll freak out, but if I don't see anything I'll freak out," Weinberger says. "It's a lose, lose situation for me."
Open-water swimming made its Olympic debut at the 2008 Summer Games in Beijing. It was held in a relatively sterile man-made rowing and canoe park.
The 2012 Olympic open-water events are in Hyde Park's Serpentine, a water-fowl pond in London's downtown.
The men and women's races are each 10 kilometres — six laps of a 1.66-kilometre loop.
The Serpentine holds few terrors other than swampy water and perhaps a bewildered duck or swan, but Weinberger feels squeamish about what's below nonetheless.
"It's only a couple metres deep, but I'm afraid to touch the bottom," he says. "It just freaks me out."
Marathon swimmers often can't see where they're going with their heads in the water, so they lift their heads up to grab both a breath and their bearings.
"We try to incorporate breaths up front, lift our heads up almost like a water polo player," Balazs explains. "We just don't keep our heads up. You lift up, look where you're going and put it back down.
"There's usually someone in front of you that you can follow and if they go off course, then we all go off course, so no one is really gaining anything."
Weinberger's coach Ron Jacks invokes the old Red Cross slogan "swim with a buddy" as a race strategy. If you swim by yourself, you might lose the race.
"One of the big things I say to the young kids is 'Don't swim alone,"' Jacks explains. "When there's 10 or 12 people navigating, the tendency is to be pretty straight. If there's one person navigating, you can be off.
"If you're dead tired and you've got half the race left, you'd better try to stay with that group because this is the most important time of your race right now."
In opaque water, it's difficult finding the most efficient line from start to finish, even with a boat guiding the swimmers. Going just a few metres off course adds unwanted distance to an already long swim.
"It happens all the time," Weinberger says. "That's the brilliant part of open-water swimming. Anything can happen. You have to deal with currents, waves, swells, boat waves."
Weinberger says it's helpful to look for large landmarks when he lifts his head. A skyscraper, mountain or boat dock provides a visual cue for navigation.
It also takes the swimmers' minds off any fish-on-fish drama.
"I'm actually scared of open water," Balazs confesses.