on
this link,
the institudo estadual do ambiente (inea)
provides the
suitability
of several
beaches on paquetá island, including
the nearby
praia da
moreninha, that can be used to
guess water quality at the praia de são roque.
constantly updated, the red flags mean that swimming is not
advisable, green flags mean waters are clean, and yellow
flags suggest using own judgment - any of rio's beaches
may have polluted
waters within 24 to 48 hours following heavy rains.
this link shows
praia de são roque on a
wikimapia.
the link is best seen using
google chrome, as it might not open correctly with other browsers.