South Island is separated from North Island by imaginary boundaries.
When New Zealand was separated from the colony of New South Wales in 1841 and established as a Crown colony in its own right, the Royal Charter effecting this provided that "the principal Islands, heretofore known as, or commonly called, the 'Northern Island', the Middle Island', and 'Stewart's Island', shall henceforward be designated and known respectively as 'New Ulster', 'New Munster', and 'New Leinster'"
 It is bordered to the north by Cook Strait, to the west by the Tasman Sea, and to the south and east by the Pacific Ocean

