GREENORE, Ireland -- The small ferry moves gently across the calm waters of Carlingford Lough, connecting the picturesque hamlet of Greencastle in Northern Ireland with the village of Greenore, a mile and a half away in the Republic of Ireland.
It began sailing a little more than two years ago, saving farmers, commuters and tourists an hour-long drive inland to the nearest bridge.
The service is another sign that the border has all but vanished since the Good Friday Agreement was signed in 1998, ending decades of sectarian violence and creating a quiet sense of normality that older generations cherish and younger people may take for granted.
But if the U.K. leaves the European Union on Oct. 31 without a Brexit divorce deal, this local boat could find itself plying an international border.
"We don't know what to expect," said Paul O'Sullivan, the ferry company's managing director. "Brexit has resulted in chaos for our company."
With both in the EU, the border barely resonates. As members, both the U.K. and Ireland have to abide by the rules of the club — the free movement of goods, services, capital and people.
In a no-deal Brexit, that all goes and the border — the only land border between the U.K. and the EU — will resonate once again.
Little wonder then that it's been the most intractable issue in the Brexit negotiations over the past three or so years since the U.K. voted to leave the EU in June 2016.
With little more than three weeks to go before the scheduled Brexit date of Oct. 31, the two sides have failed to agree on a plan to ensure the border remains open, without the checkpoints that were magnets for violence during three decades of conflict. More than 3,500 people died during "The Troubles."
"People in their 40s and 50s and older, we remember The Troubles very well," said 51-year-old Patrick Robinson, a member of Border Communities Against Brexit. "What started off as border troubles exactly like what is going to happen now escalated into what became known effectively as the civil war in Northern Ireland."
British Prime Minister Boris Johnson has said that the U.K. as a whole, including Northern Ireland which voted to remain in the EU during the referendum, has to leave on the scheduled Brexit date — with or without a deal. Not doing so, he says, would undermine faith in democracy.
That stance has raised concerns that a physical border will return and threaten the fragile peace process in Northern Ireland and the economic opportunities it has created.
No one really knows what will happen even though political leaders on all sides keep insisting the border will stay open. People are worried about the long-term impact of the potential changes.
Like many businesses, the Carlingford Lough Ferry has received little guidance: Will farmers carrying hay from the south need to declare their goods? Will there be forms? Customs officers with clipboards? And then there's the question of whether the ferry will be allowed to operate at all.
Back in the days of hard borders, trade between North and South was impeded. It took truck drivers hours to get cleared and cross to the other side. Lush rolling hills were marred by guard towers, soldiers and checkpoints. Criss-crossing the border several times a day was challenging.
The inability to no longer move freely is likely to hurt the smallest operators the most.
"The economic shock will be so great that there is no way to mitigate against the risk," warned Daniel Donnelly, a spokesman in Northern Ireland for the Federation of Small Businesses.
Even low tariffs in the event of a no-deal could wipe out the profits that small businesses with low margins make, he added.
People here just don't see any point in going back to the past. Piloting the ferry across Carlingford Lough, 31-year-old Shane Horner remembered the border checks and troops that were deployed along the border when he was a child. Crossing was slow and intimidating, he said, but "once that stopped it was grand, you could come and go as you pleased."
Today, farmers from the Republic take the new ferry service to sell silage and hay from the lush fields of County Louth to customers north of the border. Wedding parties from the North use it to cross for events in the medieval Carlingford.
It's a bus service on the water — not a stronghold between nations.
"There is a cross-community dimension," said O'Sullivan, who remembers meeting some northerners taking the ferry on their first journey across the border. "If there is a hard Brexit, it almost certainly will have an adverse impact."
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