The number of continents and planets keep changing since the big shot scientists looking to make themselves a name keep changing the definition of what constitutes a continent, planet, etc. And the definition change means either existing ones are forthwith no longer considered one. Or ones previously considered too small (or whatever other disqualifying feature excluded it) are henceforth considered one under the new definition.
Google it. What they discovered with better satellite and a very long human investigation is that New Zealand is actually the highest point of a submerged continent half the size of Australia.