First the good: our guide, Ricardo, was phenomenal. He really knew a lot of history, culture, geography, geology and we learned a lot! Swimming in the sea was one of the best things I have ever done in all of my travels. I have never seen anything like it. So blue and clear! We got to jump in and swim 5 times. It was heavenly.
Second; not bad or good parts, but things to be aware of:
1. The meeting place in Rome was a small cafe (food truck size) that was very hard to find. It was open at 6:00 am and had delicious coffee and amazing pastries, but not much else. They are cash only and do not speak English. There is a tiny bathroom down a steep spiral staircase.
2. The bus from Rome to Anzio was a standard coach/tour bus. Comfortable but no bathroom.
3. When you arrive in Anzio, you walk about 5-10 minutes to the ferry. There is no shade or waiting area on the dock. The ferry has a snack bar and bathrooms.
4. The lunch was tasty and plentiful, but it was not served until after 2 pm.
5. The boat is no frills! There is a standard cooler that could fit a few things from passengers; we put a few beers and waters in it. It has a small bathroom
6. Your stuff will get wet from all of the going back and forth from the water. Not bad, just be aware of it. Don't bring a fancy bag!
7. Bring your own water and more than you think. They have some bottled water that they pour out into mouthwash cups, but it is not enough because it is hot and a long day.
8. Bring the obvious things: hat, sunblock, swimsuit
9. Bring your own snorkel or get one from them as an add on it's worth it!
10. It is a long day and you are stuck with people who may be loud and rowdy. We had a nice mix of couples and families, but about 50% of the young people/couples acted like it was a frat party and their constant loud chatting on the bus/ferry was super annoying.
11. You have an hour ish of free time in Ponza after the boat ride before catching the ferry back. You will be wet and hot and the cafes are crowded and not air conditioned. And it will be early for dinner and many places aren't open yet. We ate a fine dining seafood place outside which was amazing, but if you only want to spend a few bucks, I'm not sure how many options there are. I didn't want to walk up a huge hill with all my wet bags to find out.
12. They didn't tell you this until after you're on the bus, but there are jellyfish and urchins to be aware of. Not dangerous if they sting you, but "uncomfortable". I saw a few and avoided them.
13. If you are expecting a coral reef full of fish to see snorkeling; don't. It's pretty bare of sea life, but that didn't matter to us! It was still amazing
The not so good:
1. The boat was packed and it is not comfortable! I was not expecting a yacht, but they packed us in like sardines - shoulder to shoulder. The seating is a few areas of park bench-style rows. Think the bed slats that come in ikea beds. Your rear end will not be happy after a few hours on those and there is not enough seating in the shade for those who want it. They should have sold 20 tickets and not 35+ to make it less terrible and crowded. It's like being in economy on an airplane but hot and wet. (It was still worth it for the swimming!)
2. The loud speaker on the boat is LOUD. If you sit anywhere near it, it will blow your ears out. Bring earplugs.
3. The ferry is hot and crowded. It has AC, but the AC in Italy is nothing like the US. It will be hot.