Ireland was always an island and was never linked by land to Britain, according to new research from the University of Ulster (UU).
Scientists have long believed that the two countries were joined by land - even myth has it that Finn McCool built a bridge to Scotland - but researchers from UU claim they have new evidence to suggest this was never the case. They also say the first inhabitants of Ireland were mariners not farmers.
Dr Andrew Cooper and his team from the Centre for Coastal and Marine Research at UU recently joined forces with the University of Maine in a bid to prove their claims.
They have been using specialist marine-coring equipment - shipped in from the United States - and a Department of Agriculture research vessel to extract samples of the seabed around the Northern Ireland coastline.
The samples will help them find out about what life was like 10,000 years ago, when the submerged land was part of the island, and when the first humans arrived in Ireland.
"At the end of the last Ice Age, sea-level in Northern Ireland was about 30 metres lower than it is now. That means the sea now covers a large area of formerly dry land.
"The submerged landscapes were dry land about 10,000 years ago, at about the same time as the first humans arrived in Ireland. People most likely lived and hunted on these ancient coastal plains." said Dr Cooper.
Dr Joseph Kelley, University of Maine added: "Our study challenges the notion of a former land bridge to Ireland to enable humans to walk from Scotland, we believe the first human inhabitants of the island were mariners."
These studies of sea level and shoreline change are part of a long-term collaboration investing similarities and differences in the marine geology of the northeastern United States and of Ireland.