Which marginal sea of the Atlantic lies between Ireland and Great Britain? The answer is the Irish Sea.
The Irish Sea separates the island of Ireland from the island of Great Britain. Its shores include the Republic of Ireland, Northern Ireland, Scotland, England and Wales, while the Isle of Man sits near its centre. The sea connects with the Atlantic system through the North Channel in the north and St George’s Channel and the Celtic Sea in the south.
This is a marginal sea rather than an enclosed lake-like basin: its waters are part of the wider North Atlantic circulation. The sea supports busy ferry and freight routes, fishing, offshore wind development and other energy infrastructure. Its geography has also made it a natural corridor for travel between Ireland and Britain for centuries.
The most common confusion is with the Celtic Sea. The Celtic Sea lies south of Ireland and west of Britain, while the Irish Sea occupies the narrower space directly between Ireland and Great Britain. The Isle of Man is in the Irish Sea but is neither Ireland nor part of Great Britain.