UI-Te-Rangiora
en.wikipedia.org
en.wikipedia.org
Also icebergs do come into New Zealand waters, and even get grounded on the continental shelf especially the larger ones which break off in slabs the size of small countries. We know that Polynesians got as far south as the Auckland Islands from archaeological remains.
I find it hard to believe that this could have occured a full ~700 years before New Zealand had its first polynesian arrivals (~1200-1300 AD).