Cook Strait splits New Zealand in half. Travelers can cross the 20 miles between the North and South Islands on large ferries and small planes. Ferries carry passengers, vehicles, freight and even trains between Wellington, at the foot of the North Island, and Picton, South Island. The journey takes three hours, including an hour in the beautiful Marlborough Sounds. A small plane can cross in 20 to 25 minutes.
Chose one of the two ferry companies, The Interislander or Bluebridge (see Resources). Both give frequent service for walk-on passengers and those taking their cars from one island to the other. There are extensive amenities on both: food, bar facilities, scenery-friendly lounges, movies and Internet access.
Book early for bargains. You may find fares on the more established and frequent Interislander about 25 percent higher than on Bluebridge (as of October 2009). Both make online booking available--nine months ahead for the Interislander and six months ahead for Bluebridge.
Arrive early, especially if you are driving a vehicle onto the ferry. Otherwise leave your rental vehicle in the designated area and walk, or trolley, your luggage to the terminal. Your printed tickets have complete directions. Street signs for "Ferry Terminal" will show the way to the Interislander. The Bluebridge's terminal is a mile away, across Waterloo Quay from Wellington Railway Station. Board the vessel when called and enjoy what "Wine Spectator" magazine calls "one of the most beautiful ferry rides in the world"--three hours of bliss on a beautiful day; not so much on a rough one.
Reverse the direction. Picton is a very small town with the terminals easily visible at the only wharf.
Investigate the price difference between flights and ferries (see Resources). Book well ahead and it might be just 50 percent more per person. Consider sailing one way and flying the return journey.