alternatively, there is a boat that leaves praça xv every 30 minutes and reaches praia de charitas in 15 minutes.  

from charitas, the bus line 33 goes along the shore stops at praia da várzea / salinas, praia do cáis, and praia de jurujuba (final stop).

praça xv is easily reachable via taxi in 15 minutes, or via several buses routing along copacabana and ipanema, including bus 354 - the metrô station estação carioca is about a 10 minute-walk away from praça xv.