the channel at the entrance of the bay is 30 meter deep and has a sandy bottom that slowly moves inward in the bay. the tides in the bay are quite calm, with waves normallyr reaching less than one meter in height, except in the occasional winter storms when polar fronts create climatic instability and stronger winds and waves.

there are a number of islands dotted around the guanabara bay, with the two most prominent being the ilha do governador (govenor island) and ilha de paquetá (paqueta island).

the biggest island in the bay, ilha do governador spans 34 square kilometers on the western side of the bay, with an estimated 250,00 inhabitants. part of the city of rio de janeiro, the island is comprised of 16 neighborhoods, whilst a large proportion of the island is taken up by the antónio carlos jobim international airport.