Handsomedan:

 

Geektastic: 

 

It would save so much traffic on the roads and so much driving time.

 

But places like Picton and Kaikoura would lose so much traffic (of the good kind) and income from tourists...at least I assume they would (I have absolutely no evidence to back that up). 

 

There have been proposals to shift the SI Cook Strait terminal to Clifford Bay, I think cost of building all-weather facilities keep killing the proposals.

Cook Strait is an "interesting" stretch of water. I made the mistake of crossing it on the Te Hukatai small cat service that ran for a short time out of Mana in the late '90s - on a day when it should not have been out there.  The "90 minute trip" took 5 hours.  There were only about a dozen passengers, some of whom were injured as they were too incapacitated with seasickness to hold on or even move seats when they'd chundered everywhere including over themselves.  The vessel was not safe for those conditions, props were way out of the water when cresting waves, by the time it was in troughs, it didn't have enough way on to cut through, one of the bows would dig in and the vessel come to a full stop before bouncing back, if there'd been an engine problem it could have gone beam on and capsized.  I believe it was only supposed to sail in conditions <3m, and they were under investigation by Maritime NZ for safety violations when the company folded.

Edit - I wanted to post a photo to avoid confusion with the much larger cats that have also been used for Cook Strait service, but can't find anything from the time, however this is the boat now: