[BradyLS]

“experts say” 300 foot tsunamis. And House Atreides says bull crap! By what mechanism would they create them?

I can think of a way. They detonate a nuclear device of enough power along a tectonic fault that it causes a submarine earthquake that releases magnitudes more energy. The quake creates the tsunami.

[House Atreides]

“...They detonate a nuclear device of enough power along a tectonic fault that it causes a submarine earthquake that releases magnitudes more energy. The quake creates the tsunami.”
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Perhaps...but VERY unlikely. There are submarine earthquakes all the time more powerful than any likely to be triggered by a thermonuclear detonation ... and they typically generate tsunamis, if they generate any at all, of several inches to 1/2 foot. As others have pointed out, the main destruction would be from blast & thermal effects as well as from radioactive fallout from vaporized ocean salt water.