It turns out that this place in Alaska called Lituya Bay has had monster tsunamis in the past. I mean really monster.
It's a long skinny bay, two miles wide at the widest and 720ft deep, that narrows down to a channel only 33ft deep where it connects to the ocean. The inland end of it has cliffs and mountains 2,500ft to 6,000ft tall looming over the waters. On July 10, 1958, there was a bit of a slosh in this giant bathtub: three thousand vertical feet of cliff face and glacier, weakened by the nearby Fairweather Fault, slid into the water on the inland end of the bay, triggering a tsunami 525m high.
That's "m" as in meters. In other words, if you could have parked that longtime standard for height comparisons, the Empire State Building, on an island in the middle of the bay, the wave would have overtopped its radio mast by more than two hundred feet, like something in a Goretopian environmental fantasy movie.
I don't care who you are, 1700ft+ waves are just cool as dammit.