these two hotels are the most convenient to são francisco beach, praia de charitas, praia do preventório, and to praia de samanguaiá, in addition to praia de salinas, praia do cais, and praia de jurujuba, that are only a 10 minute taxi ride away. 

on this link, the instituto estadual do ambiente (inea) provides the suitability of several beaches in niterói, including praia de jurujuba that can be used to guess water quality at praia do cáis since they are very close to each other.

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 do cáis on a wikimapia  - the link as we present it is best seen using google chrome, as it might not open correctly with other browsers.