Just thinking about it, it seems to me that Great Britain would take up roughly half of the Gulf (perhaps a bit less), in terms of square miles. I hadn't realized it was that young. Although, I do know from serving aboard ship there, it is a pretty shallow body of what, perhaps more shallow than any of the Great Lakes, other than Erie.
Of course, that should have been "water" not "what" - predictive typing on the smartphone strikes again.