How a landlocked Irish Sea could reshape British and Irish politics

What changes if the Irish Sea is a freshwater lake cut off at St George's Channel and the North Channel?

Britain and Ireland may integrate more closely, making an independent Ireland less likely in this counterfactual.

Closing St George's Channel and the North Channel would leave a very large freshwater lake between Britain and Ireland. The altered geography is treated as a force for earlier and more seamless political integration. In this counterfactual, a single combined state becomes more likely and an independent Ireland less likely. The answer is a broad political inference from the new geography rather than a detailed constitutional history.