More than a dozen sailboats, eight small fishing craft and a swarm of canoes were among the fleet embarking yesterday from Marina da Gloria, the inner city harbor where Olympic athletes are already preparing for the 2016 Summer Games.
Sailing under the imposing cliffs of the Sugarloaf mountain, protesters honked foghorns, blew rescue whistles and chanted "baia viva!", meaning roughly "the bay lives!"
Water quality in Guanabara has become the main concern over Brazil's preparations for the world's biggest sporting event. The city promises safe conditions, but environmental activists say the stunningly scenic Guanabara Bay is effectively a giant sewer.
Not only does a majority of the greater Rio area's sewage pour untreated into Guanabara, but dozens of rivers deliver a steady supply of trash, environmentalists say.
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According to Ricardo, in some areas of Guanabara "there's a more than one-meter thick layer of plastic at the bottom."
Rio's original bid to host the Olympics included the headline promise of cutting pollution by 80 per cent, but officials now concede this has no chance of being achieved any time soon.
"It was propaganda," Ricardo said, "a completely unrealistic goal."
"It's the most beautiful postcard in the world and it lacks just one thing - being clean," Swan, who won bronze in Beijing in 2008, said.
Environmentalists see the run-up to the Olympics as a unique - possibly final - opportunity to pressure the government into making good on a clean-up program that has been running with little effect for two decades.
Yesterday's protest would not have been immediately visible to many Rio residents, unless they were among those sunbathing on one of the nearby polluted beaches.
"That's the idea of this," said one of the organisers with the Baia Viva group, Nahyda Franca, 58. "We're one year from the Olympics and need to get attention."
The pollution is impossible to deny. Even inside Marina da Gloria yesterday raw sewage and toilet paper could be seen pouring from city drains.