Virtual water

This was a new one on me but apparently 40% of our water is now coming from some of the most at risk water areas in the third world. We import too much food which is produced for us in these countries and there are now growing (pardon the pun) concerns that this trend is not sustainable.
This got me thinking (always a bad sign) Over here in UK don’t we have too much of the stuff? Which is causing us a lot of problems. Oil tankers arrive daily at our ports unload tons of the stuff and then return home empty. Why can’t we fill em with H20 and sell it to whoever wants it. I know oil and water don’t mix but it is more than possible to devise a method of covering the tanks to allow the water to be kept clean enough for treatment at the port of arrival. Eh might earn us a few bob in foreign currency to. Or am I now totally of my trolley?