A subsea tunnel between Motutapu and Rangitoto Islands has been proposed rather than the potential move of the Auckland Port up north.  People behind the idea say that the tunnel would be considerably cheaper at $4.1 billion than moving the port from Auckland to Whangarei at a cost of $12 billion. Tunnel would also decrease pollution, transportation time, traffic congestion and make it unnecessary for port employees move or lose their jobs, they say.

Mind you that this is not an official tunnel proposal, but just a couple of fellas coming up with the idea.

https://www.scoop.co.nz/stories/BU2002/S00345/dont-move-ports-of-auckland-build-a-tunnel.htm