The story of Cook Strait ferry service begins in 1895, when the Union Steamship Company launched an overnight passenger run between Lyttelton and Wellington known as the "Steamer Express." For decades the service connected the islands reliably enough, but the 1968 sinking of the TEV Wahine in Wellington Harbour changed everything. The disaster killed 53 people and began the Steamer Express's slow decline. A replacement vessel, the TEV Rangatira, arrived in 1972, but the Union Company's insistence on steam turbo-electric power - when the rest of the industry had moved to diesel - proved a costly miscalculation. The government took control in 1974 and cancelled the service entirely by 1976. Meanwhile, New Zealand Railways had launched its own Wellington-to-Picton ferry in 1962 with the GMV Aramoana, a roll-on-roll-off combined road and rail ferry that proved an instant hit. By the 1990s, rebranded as Interislander, the service faced challengers armed with fast catamarans. Locals dubbed these newcomers "vomit comets" - a name that proved prophetic, as unreliable vessels and weather cancellations sank most competitors before they could establish themselves.

Today two operators share the route. Interislander, owned by KiwiRail, runs two ferries: the Kaiārahi ("leader") and the Kaitaki ("challenger," the largest). The Aratere, long the only vessel carrying rail wagons, was retired in 2024 as part of preparations for two new rail-capable ferries expected to enter service in 2029. Bluebridge, which evolved from Strait Shipping's freight service launched in 1992, operates the Connemara and the Livia. Together they carry passengers, cars, trucks, and the rail freight that keeps supply chains running between the islands. Booking ahead is essential during the summer peak from November to April; Christmas and New Year sailings can sell out by mid-September. Many rental car companies refuse to let vehicles cross the strait at all, since traffic flows predominantly north to south and nobody wants to pay to repatriate cars. The workaround is simple if unglamorous: drop the car at one port, walk on as a foot passenger, and collect a different car on the other side.

The crossing's scenery is the reason many travellers choose the ferry over a one-hour flight. Departing Wellington, vessels pass through the harbour and into the open strait before entering the Marlborough Sounds on the South Island side - a labyrinth of drowned river valleys where forested ridges plunge into still, deep water. The approach into Picton through Queen Charlotte Sound is routinely described as one of the most beautiful ferry journeys in the world. On calm days the water is glass and dolphins sometimes pace the bow. On rough days, the outdoor decks become obstacle courses of spray and wind, and the cinema below decks fills quickly. All ferries offer free WiFi, though it relies on mobile broadband and cuts out in the middle of the strait where cell towers cannot reach.

Cook Strait's reputation is earned. Beyond the Wahine disaster, the SS Penguin sank here in 1909. The ferries have often been the ones doing the rescuing: in 1985, the Aratika was first on the scene after a commuter aircraft crashed fatally in Tory Channel, and in 1986, the Arahura helped rescue passengers from the sinking Soviet cruise liner Mikhail Lermontov. Vehicles have gone overboard - the Aratika lost two cars in 1995, and the Straitsman lost an entire B-train truck in 2016. Insurance coverage is not automatic; by law, the maximum ferry operator liability for uninsured vehicle damage is just $2,000. The essential-items list tells the story of a crossing that demands respect: seasickness tablets, cash in case card terminals go offline, sunscreen because the New Zealand sun reflects off the water with punishing intensity, and a jacket because Wellington's wind is not a suggestion.