(CNN) -- It has become known as one the most grueling sailing competitions in the the world: a crew of two, battling alone against roaring winds and waves as tall as buildings for more than 100 days.
But the second Barcelona World Race, which is currently underway, is as much a battle of the mind as it is against the elements.
"Imagine driving a convertible car with a fireman standing on the bonnet and a hose pointed at your face -- that's what it's like on deck," said Alex Thomson, one of Britain's top yachtsmen.
The race is one of "extreme endurance and mental resilience that pushes you to right to the edge," said Thomson, who participated in the event the last time it was held but was forced to pull out of this year's competition due to appendicitis.
The endurance competition, which kicked off December 31, is the world's only "double-handed," non-stop, around-the-world yacht race. In total, the contenders will cover 25,000 miles by sail.
The nine teams participating this year are currently passing through the Southern Ocean where, according to Thomson, they will encounter "some of the most uncomfortable waters on the planet."
"It's rough and freezing cold. The cramped boat will be constantly wet and full of condensation," he said, and for more than three months, the crews won't have a second to relax.
"Any spare moments where you're not manning the sails are spent navigating, doing maintenance work, media work and trimming weight from the boat," he said.
In a competition where speed is everything, every additional gram of weight is a disadvantage. "The inside of the boat -- which you can't even stand up in - is entirely black. It's just bare carbon - even a layer of paint would add too much weight," explained Thomson.
Sinks or toilets? Forget about it. There are "none of those luxuries -- you just bucket and chuck it," he quipped.
Food could potentially use up a lot of valuable weight too, so the sailors live exclusively on a diet of freeze-fried, vacuum-packed dinners.
The competitors take turns sleeping in a shared single bed and get little more than five hours of sleep a night if they're lucky.
So how is anyone supposed to cope in such exhausting circumstances?
George Karseras is a chartered occupational psychologist who specializes in extreme sports. He says that optimizing the condition of the crew's personal relationship is even more important than optimizing the condition of the boat.
"Under intense pressures like this, cracks can quickly turn into chasms," he said. The sailors have to be like a successful married couple who have a "relationship philosophy."
Before starting their journey, the pair must "set the ground rules for how to articulate criticism, and they should always remember to express praise and support whenever it's due."
According to Karseras, studies of triathlon athletes show that those who spend time imagining exactly how tough the experience will be are often much more successful at lasting out.
"This is called 'expectation theory.' Strange as it may sound, it's very useful to immerse yourself in the worse case scenario," he said.
"If you really try and live through the most extreme terror of what you think could lie ahead, your mind is much better equipped at dealing with the reality."
However, when you're finally out in competition, positive visualizations are key. Karseras suggests keeping absolutely focused on the prize and what the achievement will mean for you and your family.
"Literally picture yourself crossing the finish line, think about your wife's smile, how proud your children will be. This helps banish the mundane stresses of the moment."
"Having a routine and absolutely sticking to it where possible is key," said Thomson. "Without it you'll lose your rhythm, focus and you'll quickly start to feel overwhelmed."
Most important in this routine is sleep and sustenance. "If you don't give yourself enough nourishment, or allow enough time to recuperate, you're being uncompetitive at best and extremely dangerous at worst."
There are some things you simply can't prepare for. Peter Nichols is the author of "A Voyage for Madmen" -- an account of how, in 1968, nine men tried to accomplish the ultimate sailor's goal: a solo, nonstop circumnavigation of the globe.
"The only man to finish was Robin Knox Johnson -- a larger than life, comic book hero of a character, who didn't have a single shred of doubt about himself," recalls Nichols.
He had the Ulysses factor -- "an otherworldly self-belief and imagination, combined with an extraordinary selfishness where everything else apart from this one goal has to take a back seat," he said.
According to Nichols this is a quality that distinguishes successful extreme sportsmen from the rest of us.
"Johnson's boat was held together with pieces of string at times. It goes to show that, at the end of the day, success has much less to do with having the right food or equipment, but the right mind."