The ocean is a hateful place, crammed from shore to shore with ill-will, bad intentions and petty squabbling. At least the water bordering Auckland is.

There, four British women have been doing their bit to pollute the beautiful blue surrounding the North Shore. "All the swearing and shouting gets dumped in the water," Penny Clark explains.

"I can get pretty annoyed with the others," Lizzie Vickers adds, "but that stays on the water."

Charlotte Dobson and Andrea Brewster separately conclude: "All our anger gets left on the water."

It is, after all, the only effective way the four women can manage their dual ambitions of wrecking each other's Olympic dreams and staying close friends at the same time.

It has been this way since Penny, 32, and Charlotte, 21, joined the laser radial class in 2005 and became contenders with Lizzie, 27, and Andrea, 25, for the solitary place in the Skandia Team GBR.

What has since transpired is a four-way competition for selection that has outlasted the other 10 Olympic classes, but, after three years of anxiety, is soon to come to an abrupt end.

On March 15, Penny, Charlotte, Lizzie and Andrea will take their dinghies out to sea and begin six days of racing at the laser radial world championships. The highest placed finisher will almost certainly compete in China. The other three will be forced to wait four years until the Games stop in London, but only after travelling to Qingdao to help their assailant prepare to live out her dreams.

"It sounds bad, put like that," said Lizzie, who is ranked at 15 in the world - the lowest of the group - and is a specialist in the heavy winds you rarely see off China.

"We live in an Olympic cycle. Four years are spent dreaming of the Olympics. I can't think about losing."

To avoid losing she has to beat Andrea, with whom she has travelled to most of Europe's sailing spots, often sharing driving responsibilities in a cramped van. She must also beat Penny, whose wedding she attended in 2006 with Andrea. Charlotte, who she describes as "lovely", must also be put to the sword.

"It's not a common situation us girls are in," explains Penny, who along with Charlotte has been named as joint-favourite by the selection committee.

"We are expected to hate each other, 'despise your enemy' kind of thing. But I like the girls. We all get on so well. We've kind of become like a family."

Charlotte adds: "We go off to Starbucks together for a gossip and a laugh. We go bowling; we've been going at it in the arcade, trying to win on the air-hockey. Everything we do, we all seem to have fun together."

Everything except sailing, that is. The women have known since September that this regatta would be used to determine the identity of Team GBR's laser radial sailor, but they have barely had a moment's peace from each other. Roughly seven weeks have since been spent in squad training in Miami, the UK and New Zealand, involving at least four of hours of sailing each day.

Charlotte continued: "When we are on the water the claws come out and we start yelling and screaming. Penny and I always yell at each other. We always get paired together in match racing and it always gets fiery. She starts complaining about some rules violation or other so I let her know my feelings on the subject."

Such feelings never last long on land. They are not allowed to.

Penny explained: "We sat down about two and a half years ago with our coach and team psychologist and worked out how we were going to get on until the Games. We drew up some ground rules in a squad charter that allows us to be really good friends on land, but sworn enemies at sea."

Andrea elaborated: "Everything has to be left at sea. When there's a dispute it has to be talked about. It cannot be allowed to fester. No cliques are allowed to form and no one is entitled to be a princess."

The success of the idea is such that the girls now train together out of choice away from squad sessions.

Charlotte said: "Sometimes it seemed really anal and over the top with all the rules, however by being like that we've managed to keep things going in a stressful environment.

"It's great to say that with days to go before we all try to ruin the other's year we are training together and going out for a Starbucks.

"We are all improving each other. Whoever goes to the Games will be much stronger for it. It's better than training with foreign sailors, helping them improve, or those who are not up to our level. This way we have all developed, remained incredibly competitive and individual, but helped improve the team's chance of winning a medal."

Penny shrewdly adds: "This way we all have an eye on each other as well.

"I know it seems strange that we can all stay such good friends in such an intense, prolonged situation. The stakes are enormous; this is what we have all been dreaming about for so long. But we've been professional and it's worked out in a way a lot of people, professional sportsmen included, just cannot understand."

It would be a perfect scenario were it not for the fear all four keep suppressed, the fear that defeat is inevitable for three of them.

None speaks of what feelings will emerge in that eventuality, when squad charters and Olympic optimism are not around to support friendship bonds which, at present, are incredibly strong.

But, as Lizzie admits, "whatever happens, Team GBR's laser radial sailor will be a lot stronger for it".

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