<font face="Verdana, Arial, Helvetica, sans-serif" size="2">Originally posted by HobokenFlyer:
Naples or Sorrento would be the starting point.
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Yes, you can take ferry/hydrofoil from Sorrento as well.
However, Sorrento is south of Naples. Getting to Sorrento from Rome would involve taking Trenitalia train from Rome to Naples, then changing for the Circumvesuviana train from Naples to Sorrento, then taking a bus or taxi from Sorrento's train station to its ferry port.
So unless you want to tour Sorrento, you should take the ferry/hydrofoil from Naples.