Global South

Op Seal: How US tried to weaponise oceans & create a horror tsunami

In the closing years of World War II, the United States, with the reluctant cooperation of New Zealand, embarked on one of the most reckless military experiments in history: Project Seal, a secret programme to develop a “tsunami bomb” — a weapon designed to wipe out entire coastal cities using nothing but water.

From Gaganauts of Geopolitics

Shocking facts

US Navy engineers, obsessed with destruction, noticed that underwater explosions sometimes produced large waves — and immediately saw a weapon in nature itself.

They quickly enlisted New Zealand scientists to turn this horrifying idea into reality.

Between 1944 and 1945, around 3,700 underwater detonations were conducted off the coast of Auckland, using explosives ranging from a few grams to hundreds of kilograms.

Their goal was to create a man‑made tsunami capable of obliterating enemy cities.

Calculations suggested that 2 million kilograms of explosives, detonated offshore in a carefully arranged pattern, could produce waves 10–12 metres high, enough to drown entire populations.

The US pursued this with clinical precision, treating civilian death tolls as mere numbers on a test log.

Preliminary tests were even carried out across the Pacific near New Caledonia, showing that the Americans were willing to spread destruction far and wide, all under the cover of “research.”

Primary target

Declassified documents confirm that Japan’s coastal cities were the main target.

The plan was simple and brutal: flood ports, bypass defences, and inflict catastrophic casualties without using atomic weapons.

Major industrial hubs, including Tokyo, Yokohama, Osaka, Kobe, and Nagasaki, were all at risk.

US planners hoped that a massive offshore detonation chain could send a 10–12 metre wave crashing into Japanese ports and cities shortly before a planned Allied invasion.

Controversies

Although official strategy papers or military directives deny this, but some sources and post‑war commentary say that a successful tsunami bomb could have been later repurposed against:

Soviet coastal cities during early Cold War planning

North Korea or China during later Pacific tensions

Any state with major coastal population centres

Why was it stopped

As the war ended and nuclear weapons became the preferred method of mass destruction, project Seal was ultimately shelved.

For decades, the US kept these files classified, concealing its willingness to weaponise nature itself.

Even today, historians warn that the “tsunami bomb” concept demonstrates how far the US military was willing to push ethical boundaries to achieve strategic dominance.