I visited the area a few years back on a cruise. We took a jet ferry from Naples to Capri and then to Sorrento. When we were in the harbor at Capri there were plenty of tour boats and charters you could go on, nothing offshore that I saw, just tourist stuff. Definately go to Capri, checking out the hardware in the marina was cool ( a buch of 100' yachts and cool euro boats). Google Capri boat rentals and you'll probably find something.