once at castelo, bus lines 322, 324, 328, and 329 reach praia do galeão in about 40 minutes. due to safety concerns, we recommend going to ilha do governador 's beaches via taxi, and / or only accompanied by a professional guide or someone familiar with the area - a taxi ride costs about br$ 70 from rio's zona sul, each way.   on this link, the institudo estadual do ambiente - inea, provides the suitability of several beaches on ilha do governador, including praia do galeão.