http://www.geosociety.org/gsatoday/archive/27/3/article/GSATG321A.1.htm

Short version: Zealandia is a continent, that 94% submerged
Long version: "A 4.9 Mkm2 region of the southwest Pacific Ocean is made up of continental crust. The region has elevated bathymetry relative to surrounding oceanic crust, diverse and silica-rich rocks, and relatively thick and low-velocity crustal structure.
Its isolation from Australia and large area support its definition as a continent—Zealandia. Zealandia was formerly part of Gondwana.
Today it is 94% submerged, mainly as a result of widespread Late Cretaceous crustal thinning preceding supercontinent breakup and consequent isostatic balance.
The identification of Zealandia as a geological continent, rather than a collection of continental islands, fragments, and slices, more correctly represents the geology of this part of Earth.
Zealandia provides a fresh context in which to investigate processes of continental rifting, thinning, and breakup."