Yes, ist is. But the tarin Circumvesiviana is absolutly save. It takes about one hor frpm, Sorrento to Napoli / Naples Main Station. There take a taxi cab; within about ten minutes you will be back at the cruise terminal. It is safer than the hydrofoil.
Here is a link to the timetable for the train from Sorrento to Naples:
Look here for the timetable hydrofoil Sorrento/Naples:
Have a nice trip