When Keri-anne Payne dives into the Serpentine on August 9, she knows she will have to be "the ruthless one" if she is to add the Olympic open water title to the world crown she won in Shanghai last year.
The Stockport ITC swimmer became the first athlete to book her place on the Great Britain team with victory in the heat off Jinshan City Beach last summer.
She said: "So many things are thrown at us on so many occasions, you just have to kind of get on with it. Because I know if I didn't do it, another 30 girls who would happily get in - maybe not happily - but they'd get in and they'd do it. You need to be the ruthless one. "
The day she booker her place the water was 30 degrees, narrowly inside the upper limit recommended by governing body FINA. Days later, 14 swimmers retired during the men's and women's 25 kilometre races when the heat and humidity, along with the high water temperature, conspired to create dangerously hot conditions.
It came less than a year after the death of United States swimmer Fran Crippen in an open water race in the heat of Dubai, prompting a report condemning inadequate safety measures and organisation.
While this represents the dangerous, and tragic, extreme of open water swimming, it is an event where the competitors have to contend with all manner of things outside their control.
Payne herself has encountered dead dogs in China, jellyfish off Melbourne and poor water conditions as well as a field of ferocious competitors.
The 24-year-old said: "I think to be an open water swimmer you have to have a certain amount of 'hard' to you. You just have to expect it... You need to get in and you need to do it and if that means swimming through jellyfish and swimming past dead animals and things, then you just have to get on with it.
"It's not something that you can think about too much. Everyone has their 'Jaws moment' when you think about it and you think 'Oh my God - no, no, no - that's it, I'm not going to think about it again. Right, just carry on swimming'.
"Sometimes if you are really worried you can strategically place yourself somewhere in the pack but other than that, you've just got to get on with it."