The edge of the continental shelfs varies from about 300 to 600 feet deep, so during the Ice Age when sea level was a few hundred feet lower, about half of the area of the continental shelfs was dry land, where today we find submerged ruins of “bronze age” vintage, often in water shallower than you’d expect at first glance, not so near the Ice Age shoreline, instead up rivers safe from ocean storms and the sea level which during the Ice Age (in the aftermath of Noah’s Flood) seemed quite unpredictable.