This helpful sign was seen at Enoshima, a popular seaside resort not too far from Tokyo.  There is even a “Billabong” surf shop there, presumably not catering to the Tsunami surfer market.  But seriously, this sign indicates that a Tsunami would flood this coastal town to 6.4m depth.  Hopefully there is also a public address system warning people to evacuate.  A monorail train station which towers above the street nearby might become popular as a refuge, although the trains are not so frequent and not very high capacity…