During the 20th century, maritime safety continued to improve. From 1909, radio became compulsory in passenger vessels over 45 metres long, and it gradually appeared in smaller coasters. Masters received more accurate weather forecasts. In the 1950s radar began to be used, and it became universal by the 1970s.
For most of the century shipwrecks were rare – usually caused by exceptional circumstances.
In 1917 the German raider Wolf reached New Zealand waters and laid mines. Three ships were sunk without loss of life. However, in June 1918 the trans-Tasman liner Wimmera hit mines laid by the Wolf, and 26 people died.
On 19 June 1940 a German raider, the Orion, sank the 13,000-ton trans-Pacific liner Niagara. The ship took with her 590 gold bars and the ship’s cat, but all people aboard were saved. A month later the Orion sank the freighter Turakina, with the loss of 35 lives. On 27 November 1940 it sank the 16,737-ton passenger liner Rangitane. Seven passengers and eight of the crew died.
In the 30 years after the Second World War there were several maritime incidents. In her first post-war voyage from Sydney to Wellington the liner Wanganella ran aground on Barrett Reef at the entrance to Wellington Harbour on 19 January 1947. It was almost two years before she was fully repaired.
In less than a decade three modern cargo carriers sank with loss of life:
- On 24 November 1959 the Holmglen sank off Timaru with all 15 lives lost. The cause was never determined, although it was possibly the shifting of deck cargo.
- The Kaitawa, a collier, sank some 15 kilometres south-west of Cape Rēinga on 23 May 1966. All 29 crew died.
- On 13 June 1968 the wheat-carrying coaster Maranui sank off the Coromandel Peninsula when her cargo shifted in a storm. Nine of the crew drowned.
On the morning of 10 April 1968 a tropical cyclone sweeping south met a southerly front, producing freak winds of up to 125 knots around Cook Strait. The Christchurch–Wellington ferry Wahine was driven onto Barrett Reef, at the entrance to Wellington Harbour.
Its starboard propeller was knocked off in collision with the reef, and its port engine was out of action. The 8,948-ton vessel drifted into the harbour before leaning to starboard. Because of the heavy list, only four of the eight lifeboats could be launched, and most of the inflatable life rafts flipped in the savage seas.
The Wahine finally capsized at 2.30 p.m. Most deaths occurred on the Eastbourne side of the harbour, where people were driven against sharp rocks by the waves. Of the 734 passengers and crew, 51 died that day, another died several weeks later and a 53rd victim died in 1990 from injuries sustained in the wreck.