The operation, called “Project Seal”, took place during the Second World War around New Caledonia and Auckland.

The weapon, which could set into motion a 33-foot tsunami that could flatten a small city, was discovered by writer and filmmaker Ray Waru as he studied old files in New Zealand’s national archives.

“Presumably if the atomic bomb had not worked as well as it did, we might have been tsunami-ing people,” Waru said.

“It was absolutely astonishing. First that anyone would come up with the idea of developing a weapon of mass destruction based on a tsunami … and also that New Zealand seems to have successfully developed it to the degree that it might have worked.”

The project began in June 1944 – about 3700 bombs were exploded in waters around New Caledonia and Whangaparaoa Peninsula, near Auckland.

Reports from New Zealand authorities found that about two million kilograms of explosives in a line about five miles from shore would get the desired result.

“If you put it in a James Bond movie it would be viewed as fantasy but it was a real thing,” Waru said.

“I only came across it because they were still vetting the report, so there it was sitting on somebody’s desk [in the archives].”

In his book Secrets And Treasures, Waru reveals other unusual findings from the archives including Defence Department records of thousands of UFO sightings by military personnel, commercial pilots and the public.

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