James Moore they work on a principle of wave forming, the frequency builds and resonates with itself. The research is on super Tsunamis which appear as a function of volume of displacement compared to the maximum wave possible in the medium of water. At a point where the internal dynamics of the wave are effectively frictionless the large displacement travels at very high speed for a distance where the phenomena can be maintained based on the volumes of water present.
Simulation shows that historical events of 100 meters over gulfs known for mantle activity, explaining high shell and sea life findings from archaeology. The speculated super Tsunamis have wave forms of 2000m based on high altitude findings in certain areas of the globe. My preferred studies show relatively small displacements causing 400m waves capable of transversing the Atlantic and maintaining speed from the fluid dynamics. Its very hard to take large pool University studies and extrapolate but the archaeology suggests these are relatively common in terms of centuries with exceptional waves matching known periods of earth activity or speculated asteroid activity.
The bomb therefore is timed to create a pressure wave below the surface at a point where the displacement will reflect the magnitude back from the sea floor creating the low friction turbulance the super waves require. I have only read interpreted reports but the US tests in the Pacific started the bad idea and warmongers are stupid, so they probably followed through. I imagine all sides will have an idea of how to do this.