Top-secret wartime experiments were conducted off the coast of Auckland to perfect a tidal wave bomb, declassified files reveal.

An Auckland University professor seconded to the Army set off a series of underwater explosions triggering mini-tidal waves at Whangaparaoa in 1944 and 1945.

Professor Thomas Leech's work was considered so significant that United States defence chiefs said that if the project had been completed before the end of the war it could have played a role as effective as that of the atom bomb.

Details of the tsunami bomb, known as Project Seal, are contained in 53-year-old documents released by the Ministry of Foreign Affairs and Trade.

Papers stamped "top secret" show the US and British military were eager for Seal to be developed in the post-war years too. They even considered sending Professor Leech to Bikini Atoll to view the US nuclear tests and see if they had any application to his work.

He did not make the visit, although a member of the US board of assessors of atomic tests, Dr Karl Compton, was sent to New Zealand.

"Dr Compton is impressed with Professor Leech's deductions on the Seal project and is prepared to recommend to the Joint Chiefs of Staff that all technical data from the test relevant to the Seal project should be made available to the New Zealand Government for further study by Professor Leech," said a July 1946 letter from Washington to Wellington.

Professor Leech, who died in his native Australia in 1973, was the university's dean of engineering from 1940 to 1950.

News of his being awarded a CBE in 1947 for research on a weapon led to speculation in newspapers around the world about what was being developed.

Though high-ranking New Zealand and US officers spoke out in support of the research, no details of it were released because the work was on-going.

A former colleague of Professor Leech, Neil Kirton, told the Weekend Herald that the experiments involved laying a pattern of explosives underwater to create a tsunami.

Small-scale explosions were carried out in the Pacific and off Whangaparaoa, which at the time was controlled by the Army.

It is unclear what happened to Project Seal once the final report was forwarded to Wellington Defence Headquarters late in the 1940s.

The bomb was never tested on a full scale, and Mr Kirton doubts that Aucklanders would have noticed the trials.

"Whether it could ever be resurrected ... Under some circumstances I think it could be devastating."

[Editors note. If you have any further information or details relating to this article, please send to emailtom@cox.net]