Great advice, hikermor! Geezer in chief strikes again!

For comparison, it appears the tsunami resulting from the Krakatoa eruption in 1883 were 40 meters tall (= 131 ft). I'm guessing a 400' tsunami requires not just 3 times as much energy, but an exponentially greater amount. I guess if I were in the path of such a tsunami, I'd just try to take a selfie with the incoming tsunami and post it online before I die.

http://volcano.oregonstate.edu/tsunamis