Beaches While In Rome!
 

We have 4 Days availabe in Rome and I was wondering if anyone has a day trip to the beach they can suggest. We will be staying at the Spanish Step area. Please include a suggestion of transportation. ;-)

We stayed a week in Livinio a few years ago and enjoyed the beach there, but you can take a train to several nice beach towns south of Rome. I believe the same train we took back and forth to Rome went further south to Sperlonga, for example, which had an excellent beach. We also liked the beach at Gaeta. The beach towns just south of Rome - that is, north of Livinio- looked a bit tacky to us, so you might plan to go at least as far south as Livinio.

StCirq: Pay attention: what you mean for Livinio is actually LAVINIO LIDO. Livinio is a mountain resort in north Italy!!!! (My grandpa lived in Lavinio, and I spent several summers there when I was a kid).
I suggest other beaches that are closer to Rome: Ostia, Ladispoli, Santa Marinella and Fregene. They are the beaches where the romans usually go in Summer for a short daily escapade when their holidays havent started yet. Sperlonga and Gaeta are actually about 100 kilometres from Rome so actually you should rent a car and start VERY early in the morning to reach these beaches, so I dont know how convenient it should be, considering that the LITORANEA or Via Severiana (road that goes southwards along the coast of Lazio) is usually pretty conjested in Summer).
DONT stop in Torvajanica, please because it is a dump!
Close to Lavinio there is also Lido dei Pini and Adrea, not that bad.

Lavinio, Lavinio, Lavinio, Lavinio...I think I've got it now.

Hehehe! Just wanted to point it out because Lavinio is on the sea and Livigno is on the mountain! (in Lombardia, near the Swiss border).

As you're using public transport I may suggest you these easy-to-get-to places :

Ostia Lido : Not bad, sandy beaches, public or private resorts but quite crowded during weekends.
How to get there : Metro A / B to Piramide then
Train to Lido di Ostia (every 15 mins) until its last station (30 mins).
Many resorts just in front of the station or take bus 07 (zero-seven) to the municipal free entrance beaches of CastelPorziano . A family place among the dunes . Ask for "i cancelli" (gates).
If you go further south you can find some nudism but same crowds as above.
City "Metrebus" fares apply : A day ticket for 3.10 euro gives you the right to travel all over the route.

Santa Marinella : nice place, gravel and sandy beaches, clean water.
One hour travel by train.
Hourly services to Civitavecchia from Termini/Ostiense/San Pietro stations.

Fregene : a little bit more upper class sandy beaches and nice resorts with good restaurants on the beach.
Blue Bus from Lepanto metro station (1 hr).
Last bus back at 7.20PM

The summer season here lasts from May, 1st until September 30th.