The body of water that separates the United Kingdom from Ireland is the Irish Sea. This body of water extends approximately 140 miles and serves as a natural boundary between the two regions. The Irish Sea plays a crucial role in maritime activities, including trade and transportation, with ferry services connecting various ports. Additionally, it is home to diverse marine life, with its unique ecosystems supporting various species. The sea's strategic location has also shaped the historical and cultural interactions between the United Kingdom and Ireland.