In the 8th century, the Saracens moved through the area and sacked the city. It never recovered, and was ultimately abandoned sometime around 1500. It was inevitable, though, as waters were rising and slowly flooding the city, which had already sat low on the bay. The volcanic vents that had been such a draw to the city in the first place were shifting; other cities in the area, like Pozzuoli and Miseno, were also sunk beneath the waves.
Now, the entire site is an archaeological dive site, where visitors can take a boat tour above the ruins or even scuba dive through them..