on this link by grupo ccr it is possible to check the schedule of boats going to praia de charitas by clicking on linhas, horários e tarifas on the top of the page.

to check the return schedule, clicking on 'charitas' on the map, and selecting 'rio de janeiro' in the submenu opens the schedule, where the fares are also listed.

this beach is normally not visited by travelers vacation in rio de janeiro, however it can be an interesting alternative to people seeking a different perspective of guanabara bay.