The longest pool race, the 1500m, is swum in a prelims/finals format at a FINA World Championships, with the top eight from the heats advancing to the final 18 hours later. In any open water race, there is only one swim to determine the medalists, so preparation in and out of the water is crucial to optimal raceday performance.

On Wednesday, the women raced the 10K at 8:00 a.m. with the men following at 12:00 p.m. Race day prep can differ from the pool races with the open water race being much longer, and in a hotter environment. The water temperature measured by the FINA Officials before the race was 27.3 Celsius and the air temperature at the start of the race was 26.

Women’s 10K gold medalist Sharon van Rouwendaal of the Netherlands detailed her morning routine leading up to the race, which started at a 5:30 a.m. bus trip from the hotel to the venue.

“We have breakfast on the bus because breakfast is not open in the hotels (yet),” van Rouwendaal said. “Then we check-in and get our numbers and our transponders, and they check our fingernails. And if everything is correct and approved then we start our own preparations.

“I usually do dryland and some stretching and mostly I go in the water to wake up a little - it's just a little sprint, just 10 minutes in the water and to cool down (from the sun) so that afterwards I can put on my suit without it being too hot. Afterwards, we put the transponder on, and then it's last-minute preparations with the suit and the vaseline and it's time to go.”

Silver medalist Leonie Beck of Germany had her alarm set for 4:37 a.m. and hit snooze for 10 minutes before rising. The hardest challenge on race day, both Beck and van Rouwendaal admitted, was finding enough food to eat.

“At 5 a.m. you are already excited but you have to eat because it is a hard sport,” Beck said. “Not eating is worse because in the end (of the race) there is no energy in your body. We try our best to eat as much as possible in the morning and then we prepare and concentrate, and go through the race.”

Air temperatures in Budapest got as high as 35 degrees during the day, so eating and hydrating is crucial for the athletes in such a gruelling race. With the race being over two hours, the athletes take time during the race at the “feeding dock” to quickly drink their desired fluid to help replenish anything lost during the two-hour race. The one-hour 5km race does not feature the feeding dock, so getting a good breakfast before the race is important to have enough energy to swim the 10K, but normal race day anxieties can make that a challenge.

"That's the hardest thing, to eat a lot before a race because you have that sort of competition feeling and that feeling in your stomach that you're not really hungry but you have to eat,” van Rouwendaal said. “I ate in the bus and in my room before, and I try to eat every 30 minutes afterwards but I really don't want to eat, and I am drinking it away with water to get something in.

Both van Rouwendaal and Beck decided on a small, but healthy breakfast before the 10K.

"This morning it was something that I like - bread with Nutella and bananas,” van Rouwendaal said. “Some typical Dutch breakfast. Normally I would like to have bread and eggs and bacon but it's too much and it's going to go out anyway. I try to just eat something that I look forward to eating and it's not the best option, nutella, but this morning it was the only thing I could eat.”

"I usually also eat bread with Nutella and that's something I like,” Beck said. “I love Nutella and at 5 a.m. it's also hard for me to eat but it is better than nothing. What's really hard is I try to eat corn with milk so it's like baby food. It's really disgusting but it's healthy and it helps to perform.”

The men’s race started later in the day at 12 noon, and the Italian gold and silver medalists, Gregorio Paltrinieri and Domenico Acerenza woke up at 8:30.

"I had a big bowl of yoghurt with cereal and then I had three (slices of) bread with marmalade and then I had a cappuccino and eggs,” Paltrinieri said. “A lot of things.”

"It was a typical Italian breakfast!” Acerenza joked.

"Everything I saw, I took it, just in case!” Paltrinieri added.

Paltrinieri admits he didn’t jump in the water at all before the race, doing his entire warm-up routine on land that started when he arrived at 10:20 a.m. Due to the heat rising throughout the morning, he stayed in the air conditioning for as long as he could before the race started.

Bronze medalist Florian Wellbrock of Germany took a different approach - he swam a short pool warm-up of 400 meters to wake himself up.

“It's not a lot but I just jumped in and hopefully had a good feel (for the water),” Wellbrock said.

With the race being two hours, a lot of athletes use the first lap of the six-lap course to warm up into the race. It’s rare if someone can break away that early in the race and stay away from everyone else. With strategy playing such a huge role, many of the swimmers don’t make their move until lap four or five, well over an hour into the race.

The 10km is tactical, and the preparation is vital. The best swimmers may not warm up before the race begins, but they are strategic in everything else leading up to the race.