Most Olympic rowers have spent months fretting and prepping about the dangers of Zika-infested mosquitos and adenoviruses lurking in the Lagoa Rodrigo de Freitas. Few, though, were ready to face vicious crosswinds and waters so choppy that it left a Serbian boat capsized and others claiming these were the worst conditions they had ever encountered.

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Matt Smith, the executive director of rowing’s governing body, Fisa, defended the decision not to postpone racing – but warned rowers that conditions were likely to get even worse on Sunday, Monday and Tuesday, which could even lead to rounds being cancelled.

“It’s a small regatta, with 550 rowers, so we can pretty easily make up one day,” he said. “But if we get two or three knocked out then we go into contingency mode, and into scenarios where we possible drop rounds. We told team managers on Thursday that if you lose rounds of racing, your results from previous races could determine your placement in finals or semi-finals. They are on notice that every race matters because if we lose two or three days’ racing it could be the case.”

Smith was speaking after loud complaints about racing on the opening day being allowed to go ahead, despite the weather, which led to several rowers nearly capsizing before the Serbian men’s pair of Milos Vasic and Nenad Bedik went into the water when their boat caught a crab. Usually rowers have to finish the course to be allowed to race again in the repechage. Fisa, however, ruled that because of the conditions and the fact they were behind in the schedule, the rowers could take a DNF – did not finish – and still compete in the repechage on Sunday at 9.30am.

Fisa also denied that the Serbians faced any dangers from falling into the water. “It is nearly drinking water,” Smith said. “It’s swimming quality. It’s really good. Some might say there are viruses there, but it’s amazingly good right now.”

Most rowers did not take such a rosy view. The Australian Kim Brennan, a competitor in single sculls, was a particularly vociferous critic, insisting the course was “not rowable”.

“I do think it should have been called off,” she said. “And speaking to a lot of rowers in the boat park there’s a lot of discontent. We’ve put 10 years plus into this and to have it decided on a little bit of lottery, and what waves hit a boat at a particular time, is a little bit disappointing.”

Every race had its dramas that went beyond seeing who would cross the line first. At one point, the American sculler Genevra Stone nearly sunk like, well, a stone. While the Egyptian sculler Nadia Negm reckoned the conditions were the worst in which she had rowed.

“I actually thought I was going to sink it was so rough,” Negm said. “At one point, just past 1,000m, there were these huge waves and a full one came right into my boat and the water was up to my seat. I was 100% sure I was going to sink, and then another wave came up and I just stopped and froze. Thank God I didn’t go under. It’s the toughest conditions I have ever rowed in. It was really intense. I wish the rest of the racers good luck – if you are rowing this week you better know how to swim.”

Meanwhile, the Irish sculler Sanita Puspure, who finished one place ahead of Negm in second, described the conditions as “horrific”.

She said: “It was like sailing, surfing, everything all in one and a bit of rowing in the end. I was just thrown around with the wind. I couldn’t get the blades in at the same time. At one stage I was blown parallel to the racing lane so I had to tack with one arm into the lane, which is probably unseen before – a person doing one-arm rowing during a race. I was pretty helpless.”

But Britain’s Kath Grainger – who, along with her partner, Vicky Thornley, qualified for the double sculls semi‑finals by finishing second in her heat – disagreed. While saying that it was “the worst Olympic conditions I have raced in”, she felt it was right to race on. “If the regatta runs you have to race in whatever the conditions are,” she insisted.

The British sculler Alan Campbell, who looked particularly impressive in winning his heat, claimed the conditions reminded him of coastal rowing. He said: “I thought I must be losing time and I looked around and there was a blade in the air and one down there.”

“The wind comes down from the mountain,” he added, pointing to the most famous landmark on the Rio skyline. “Christ The Redeemer needs to spread his arms out a little more.”