Ciao,
Just happen to be looking at European diving and saw your thread. We'll I'm from a city about 60km north West on the western coast called Civitavecchia. I was born there and travel back every summer. I've spear fished there for the last 20 years and the Terranian coast line of that area is pretty nice for top and bottom enjoyment.
Diving is nice, waters are calm durring the summer, July is the best time, and very slow or no currents at all. Off the coast of Civitavecchia, literly about 1km out of Port Riva di Triano there is a WWII wreck split in half at about 100ft, the reefs are not like in the Floriday Keys or Tropics, but there are very nice wall dives, the reefs are volcanic with millions of cracks and holes where you'll find Grouper, Lobsters, Scorpian fish, octopus hanging out. Water vis is about 30 ~ 100ft depending. Temp at bottom about <70 in July so a 5mm/hoody/gloves/boots is a must.
Diving gets better and better from Civitavecchia going north to the French Rivera or from Naples going south. From Civitavecchia going north to Mt. Argentario at Port Ercole there a few dive shops and should be pretty good diving there.
The most intersting thing is on any given dive you may come across Roman artifacts. Years back we found a Roman anchor, many times I find pottery, etc.
You can get to Civitavecchia by train from Termini station or by car. About 1hr traveling. Port Riva di Triano is right off the Via Aurelia road or just a km or two away from the Autostrada exit to Civitavecchia Sud.
Here are the two dive shops I've dove with many times in the past at the port of Triano. Good outfits but call in advance to set up an appointment as many times durring the summer they are on dive trips to Egypt. Good luck
cic
Gruppo Nasim - Corsi SUB Roma
Rob