The skiffs, with their giant spinnakers and black sails towering over other boats as they speed along at full throttle, are the big beasts of Olympic sailing.

The 49er men's boat and the smaller 49erFX sail used by women are both flighty crafts that will topple over without their crews on board at the slightest breeze.

It's a fast boat but you have to work together closely to get it around the course. Rebecca Netzler, 29, a Swedish skiff team member said that if you don't sail together with the other person on board it will capsize.

Skiff sailing requires a high level of physical fitness, agility and strength. It also demands that you consume a lot of carbohydrates, especially when racing in bad weather.

In a pre-Games' interview, Dominik Buksak said that he combined his sailing with a lot weight training and cycling.

Buksak explained that if you do not reach a certain fitness level, you will be unable to maneuver and sail the boat.

The first day of the Games will see both fleets line up, with fierce rivalry on the water and close relationships developed through training and competition.

When asked about their rivalry, Vilma Boubeck, 26, the Swedish skiff's captain said: "We push each other hard during training and then we can have a coffee together or do something else in our free time."

Many of the sailors have to balance competing demands because they are closely linked with both the America's Cup, which will be held in Barcelona next year, and the SailGP circuit.

Bobeck and Netzler are both competing for Swedish Challenge at the inaugural Women's America's Cup, which will take place in September.

The Spanish men's team, who won the $2 million grand finale of Sail GP in San Francisco, is now on their way to Marseille.

Diego Botin and Florian Trittel, the crew of the Spanish 49er skipper Diego Botin who won the SailGP with his crew, said that they set themselves the goal of Olympic Gold at the start of the campaign.

The duo of both 30 year olds knows that they still have to make some crucial decisions in order for them to reach the podium.

It's impossible for an Olympic Games to run perfectly. Trittel said that in those moments of adversity the person who knows how to handle them will come out on top. (Reporting and editing by Alexander Smith)