South Korean sailor Ha Jee-min has been coming to Rio de Janeiro for three years for competitions, and he remembers seeing debris floating in the polluted waters of the Brazilian city.

But when he began his Olympic campaign Monday in the Laser event at Marina da Gloria -- the starting point for sailing events in Guanabara Bay -- Ha found the waters "very clean."

"My first year here, the waters were extremely bad, and there were sofas in them," Ha said. "But they weren't so bad in my second year. This year, they're really good, perhaps even cleaner than in Korea."

Competing in his third consecutive Olympics, Ha said he arrived in Rio on July 1 in preparation. And the water quality has been improving almost by the day, he said.

According to reports, Rio authorities have placed nets across waters to keep the garbage from interrupting races, and garbage-collecting boats have been trying to pick up pieces that escape.

Earlier this month, a study commissioned by The Associated Press showed Rio's "filthy" waterways were contaminated with dangerous viruses and bacteria, and posed serious health risks for athletes.

It said those who ingest only three teaspoons of water would be infected with viruses that can cause stomach and respiratory diseases.

With the competition underway, South Koreans and other sailors alike gave their stamp of approval.

"I have to put my hand into the water during the race, and other than a few leaves, there is no garbage," said Lee Tae-hoon, who entered the men's RS:X event. "I know people are worried about it, but they really don't have to."

Pedro Pascal of the United States, competing in Laser, told AFP: "This is like perfect conditions. You can't get better than this. It's beautiful, as you can see."

In a DPA report on the water quality, Max Groy, coach of the German 49er class team, said, "At one meter depth, we can see the bottom. This is sensational, compared with all previous experience here." (Yonhap)