Emily Bourke reported this story on Thursday, January 3, 2013 08:18:00

BRENDAN TREMBATH: It's been revealed that the United States and New Zealand conducted secret tests in the 1940s of a 'tsunami bomb' designed to inundate coastal cities.



Thousands of underwater tests were carried out near Auckland during the Second World War and showed such a weapon was feasible.



The top-secret operation code-named, ''Project Seal'', was shelved just months before the atomic bomb was used on Japan in 1945.



The secret plans have been uncovered during research by a New Zealand author and filmmaker, Ray Waru. He's speaking here with AM's Emily Bourke.



RAY WARU: I came across actually by chance a series of Project Seal reports that were made a long time after the war that were sitting on the desk of a man who was vetting military material and I said what's this and he said oh well this is the best kept secret of World War II. We were going to make a tsunami bomb.



EMILY BOURKE: Were the tests actually carried out?



RAY WARU: Yes, in fact the tests were almost carried out to completion in the sense that the programs that had been set up in 1944 were actually almost completed. They were wound down when a slightly more effective bomb, a nuclear weapon, was invented and it was clear that the war was coming to an end.



EMILY BOURKE: Where were these tests carried out?



RAY WARU: They were carried out at one of Auckland's and one of New Zealand's most well-known holiday spots, the Whangaparaoa Peninsula just north of Auckland and over a period of several months they carried out almost 4,000 test explosions to kind of calibrate the size of the explosions, the number of explosions and the depth of the explosion in the water would need to be in order to create a tsunami effect.



EMILY BOURKE: Was there any damage that occurred as a result of the research and those tests?



RAY WARU: No. They never actually produced a tidal wave. They decided at the end if there were 2 million kilograms and they were detonated in an array a specific number of kilometres from the shore that they would produce a wave that wave about ten or 12 I think metres in height and that would have been enough to wash out a shore installation. So they got quite close to doing it but in fact according to reports anyway, nobody ever tried to wipe out Auckland with a tsunami bomb.



EMILY BOURKE: Were there any targets in mind?



RAY WARU: The report doesn't specify any. At that stage I guess the military establishment would have had notional targets in mind, presumably the primary target would have been Japan, presumably coastal cities and coastal fortifications in Japan and presumably the tsunami bomb could have been seen as a weapon that would paved the way for an invasion of the Japanese home islands.



EMILY BOURKE: Were these tests carried out at the behest of the United States? Did the United States fund it?



RAY WARU: Yes they were. They were carried out at the behest of the United States. They were carried out with the full cooperation of the New Zealand government. The New Zealand government apparently provided most of the logistics, they obviously provided the location, but the Americans provided a lot of the technologies.



EMILY BOURKE: Is there an explanation of why New Zealand took part?



RAY WARU: From my research, no. I mean it was suggested to the New Zealand government that New Zealand might be a useful location. The Americans probably weren't going to do it in the Pacific. They obviously needed a kind of a military establishment that could get behind it so I guess the choice could have been either Australia or New Zealand.



Why they chose New Zealand I'm not sure. It may actually have been coincidence because there were New Zealanders involved with the kind of clearing operations as I understand it and it may simply have just come back to the New Zealand cabinet.



Certainly when it was mentioned to the New Zealand cabinet, the war cabinet at the tim, there was cooperation and encouragement so I guess it - the ball rolled on from there.



BRENDAN TREMBATH: Ray Waru, New Zealand filmmaker and author of Secrets and Treasures. Emily Bourke was our reporter.