This report of a snorkeler mistaken for a nutria and shot by a hunter (or at least some guy with a .22) has an oddly familiar ring to it. Except possibly for the meth/pot angle.
Kudos to CNN for their prompt placement of the nutria between the muskrat and beaver on the Aquatic Rodent Size Continuum. However, large swathes of the world are shown as "data unavailable" in the Wikipedia entry linked above. It is not enough to know that they haven't made it to Australia or Antarctica. Britain is safe, but JJV could have told you that.