All continents are actually bigger than they appear. Somewhere, some part of each of our continents is submerged. We know this from the treasure trove of underwater villages found all over the world.
And it makes sense; erosion, climate change, the rising and falling of ocean levels, the changes made to land masses by volcanoes and earthquakes, etc. They all impact how much land is visible in a continent.
In theory, we have 7 continents. Some people argue for 6 because Asia and Europe are actually a single landmass. However, the removal of a continent is far less extreme than the discovery of one… Which might have happened.
New Zealand, New Caledonia, and a chain of islands sits of the coast of Australia and have always been considered island nations, not associated with a continent except on special occasions when it gets lumped into the Australian continent (like Madagascar is only sometimes considered part of the African Continent).
However, new geologic evidence suggests that this area is actually a submerged continent, distinct from Australia with New Zealand, New Caledonia, and the islands the only visible traces of it. What they have found is a giant submerged landmass that has the same density of continents, but only the high plains regions are above water.
This is significant. Islands have stable bases, but they go to the bed of the sea. New Zealand doesn’t have this. Instead, it appears to have a stable base that goes into a much larger stable base below the surface of the ocean and that larger base connects to New Caledonia and a specific island chain. Then that larger stable base goes into the ocean. The exact same way a continent connects to the ocean floor. It would be the equivalent of flooding the US with close to a mile of ocean water. We’d have islands from some of our mountains, but we’d have plateaus that also rise above the water line in the form of places like Denver, Colorado.
We have trouble exploring in depths like a mile or two under the surface of the ocean. We can do it, but at great risk. Go three or four miles under and the problems compound exponentially. It’s why we really do know more about the moon than the oceans on Earth. So theoretically, if ocean levels were high enough, Denver and a few other places would appear to be islands, not parts of a continent.
So will we start to see the continent of Zealandia showing up on maps and text books any time soon? Probably not. We abhor rewriting history.