Angra dos Reis is mainly a launching port to the islands, and thus a boat is mandatory.
Of course, the harbour is full of boats, available to book under many conditions. You just have to search for your best option and bargain it.
The same program, with less options, may be made from the other side of the bay, in Parati. We did it, and had a nice trip and swim.
that's what i have found, but look at the boats going from mangaratiba, even though they don't suggest it...if you need a different time.
here's another one. looks like monday through friday, it leaves at 1530 hrs.
saturday and sundays and holidays, 1330.
The islands in Angra are relatively close to each other, so you can arrange a boat to take you for some "island hopping" during one day...Boat trips around Angra are extremely easy to be arranged, since it´s the most important mean of transportation for the locals.
The best way to visit the bay in my opinion, is to reserve 3 to 4 days around the region, arrive in the city of Angra, get directly from the pier to Ilha Grande (the biggest island in the bay) and get a boat from this island to take you to the other islands.
Prices varry much according to the season and the number of people available, but it´s usually 20-30 reais (10 to 15 dollars) each person for a whole day inside the boat. You can either make this trip through the agencies scattered in the main village Abraao, or, if you are in a big group of people, find a boat to make the tour just for your group (if you are in more than five, the price will be the same, and you have the advantage to arrive at the time you want and choose the islands you want to see). Unlike other places in Rio and Brazil, the sailorman are usualy very honest and tend to charge the same price for locals and foreigners.
The bay is usually very calm, and the boats are simple, but all equiped with safety belts and radio. Most of the sailorman are very concerned with safety, so that they never get outside of the bay to the open ocean. If you want to check the open sea side of Ilha grande, you´ll have to arrange a speedboat for you.
Go by the "Costa Verde" buses to/from Angra -they are air-conditioned, have comfortable seats and the price is very reasonable -ie. around 6 reals for 25 km (sometimes they run a discount).
Always negotiate the price with the driver, no matter what means of transportation you choose.
Angra is 153km from Rio,380km from Sao Paulo and 573km from Belo Horizonte,cities from where you can take a bus to Angra.
The central bus station in Angra is situated at Chacara beach,near "Pirata's Mall",about 2,5km from the city center.
The bus station has a big parking area and a taxi station.
The bus company that runs buses from/ to Angra - Rio(and so as for Caxias,Qeimados,Campo Grande and Nova Iguacu) is called "Costa Verde",from/to Angra- Sao Paulo is called "Reunidas" and from/to Angra-Belo Horizonte "Util".
The freeway that access Angra is BR-101(road from/to Rio-Santos).
In Angra there are many long term parks you can leave safely your car to take the boat to the islands or specificaly to Ilha Grande.
The boats leave Angra to Abrao island in Ilha Grande.