The cheapest way to travel between the North and South Islands of New Zealand depends on your flexibility and whether you have a vehicle. For "walk-on" passengers without a car, the Interislander or Bluebridge ferries often provide the most consistent value, with "Web Saver" fares starting as low as $38 to $65 NZD if booked well in advance. However, if you are a solo traveler without a car, flying can often be even cheaper than the ferry. Low-cost airlines like Jetstar frequently offer "one-way" deals between Wellington (North) and Christchurch or Nelson (South) for as little as $35 to $49 NZD during sales. If you are doing a road trip, many rental car companies offer "relocation" deals where you can drive a car one-way for free (or for $1 a day) and they may even cover your ferry ticket. For those on an absolute shoestring budget, taking an InterCity bus to Wellington and then walking onto the ferry remains the most reliable way to cross the Cook Strait for under $100 NZD total, including the scenic 3.5-hour cruise through the Marlborough Sounds.