Total war, such as WW2, pushes weapon development along all sorts of paths. The atomic bomb was the ultimate development which overshadowed all others. One discontinued path was the Tsunami Bomb.
During the war, a US Navy officer noticed wave actions created by blasting through coral reefs, a wartime expedient that would horrify environmentalists today. In 1944, the US teamed up with New Zealand at the University of Auckland to study the effects and possibly recommend a course of action. It was found to be feasible, but the amount of explosives necessary to create a modest tsunami could just as well have been dropped on the coastal city in question doing more damage than any tsunami.
The idea of a Tsunami bomb still thrills conspiracy theorists, who contend that an evil consortium of India, US and Israel detonated a nuclear bomb underwater causing the 2004 Indian Ocean Tsunami. With all the nuclear watchdog stuff going on around the globe, this does seem highly unlikely, and no sane nation would embark on such a path. However, just cruising the headlines, sanity seems to be in short supply.