Sato had survived a big tsunami before. In 1960, when he was eight, a 14-foot wave killed 41 people in Minamisanriku. The seawall was built after that, to a height of 5.5 meters, a little over 18 ...

He’s strolling the shores of an indoor ocean—a 12-million-gallon, football-field-size pool at the Naval Surface Warfare Center in the Maryland suburbs of Washington, D.C.