It’s in an area which flooded at the end of the last ice age. And that was about 10,000 years ago.
No, it’s an area some people think flooded at that time, but other evidence indicates they are mistaken.
So they say. But it could have also been a victim of a huge subsidence quake within the last 5,000 years that dropped it from say, 25 feet above sea level to 120 feet underwater. The tsunami resulting on the adjoining land which remained above sea level would have killed most or all of the nearby population, and the city would have been forgotten in the day to day struggle for survival over the next 20-50-100 years.
If it was simply flooding, the buildings would be more preserved; a quake with subsidence would have collapsed them to rubble. Which is the case here?