If you are already in Brazil, do not miss Fernando De Noronha. Actually ifyou are coming from anywhere else it is worth to fly to FDN. Prices may sound pricey but so is staying anddiving anywhere else in Brazil for the past couple of years.
Visibility is endless year round and water temps when I wasthere in January 2010 was 29-31°C, there are many little and big animals andgreat rock formations. We had dolphinsdiving with us during the first 2 days. Wedid 12 dives there and each of them were different. There are depths for recreational dives and deeper. The islandnor the diving is crowded because entrance to the island is highlyregulated. So if you want to go aroundChristmas time make sure that you make your accommodation and flight reservationsnow. And you will need these reservations in orderto be allowed into the island.
We dove with Aguas Claras and got a flight/dive and accommodationpackage which worked out very well. We had always two divemaster with us oneach dive and the boat was fast and enough room for all divers to becomfortable. Every morning they would pickus up from the Posada (Inn) to take us to the boat. Food is reasonably priced, and I recommend thatyou rent a buggy to get around the island. There are great many beaches you can visitafter the dives to relax and also to get into town for lunch/dinner. There is an ATM at the airport that acceptsinternational cards. The ones in townwhere only local - at least 2 yearsago. Make sure you have some cash with you. Even if most places take MC/Visa, there are still shops/restaurants left that are cash only.
Hope you can make it there - it is worth the extra splurge.