New Zealand author and film-maker Ray Waru has examined military files buried in the national archives and found that a top secret operation, code-named "Project Seal", set out to test  a 'tsunami bomb' doomsday device - one of many secret super weapons researched by the Allies and Axis powers during the war.

About 3,700 bombs were tested, first in New Caledonia and later at Whangaparaoa Peninsula, near Auckland. The testing concluded the weapon was feasible and that a series of 10 large offshore blasts could potentially create a 33-foot tsunami capable of inundating a small city.

Waru said though the testing was positive the project was shelved in early 1945. Experts concluded that single explosions were not powerful enough and a successful tsunami bomb would require about 2 million kilograms of explosive arrayed in a line about five miles from shore.  New Zealand authorities continued to produce reports on the experiments into the 1950s.

'Tsunami bomb' tested off New Zealand coast by Jonathan Pearlman, The Telegraph