RIO DE JANEIRO - When wind and rough seas drove the Canadian sailing ship carrying dozens of teenage students to lean precariously to one side, the captain figured it was just another day of sailing in rough weather.

When the boat immediately keeled again, he knew it was going down.

"The ship had gone from sailing upright to being on her side in the water in about 15 or 20 seconds," William Curry said. "I knew, of course, that the blow to the ship was fatal and that she was not going to right."

Just like that, a five-month academic dream cruise for 64 young students and crew ended in a mad scramble for life rafts as the SV Concordia was quickly sucked beneath the waves. Back on land Saturday, they recounted how fears of starvation and a lonely death far from land filled their heads during two nightmarish days adrift at sea.

Curry called it a miracle that everyone on board made it into rafts and survived after the three-masted Concordia apparently experienced a weather phenomenon known as a "microburst" - a sudden, violent downdraft of wind - that instantly crippled the vessel Wednesday.

The gust that knocked the ship on its side came so suddenly there was no time to radio for help before all communications equipment was submerged and ruined. So hope rested on a distress beacon that launched automatically when the vessel capsized.

"My biggest fear was that nobody knew we had sunk," said 17-year-old Keaton Farwell of Toronto. "We thought our signal had failed and nobody knew and it could be weeks before we were saved. The worst life-and-death thoughts were going through our heads, and everybody was panicking."

After 30 hours in life rafts 300 miles off Brazil, hope arrived as "a light in the sky" - a Brazilian air force jet flying high overhead sent to search the area after the beacon was finally detected.

"When we saw the plane, we were crying because of happiness. We knew somebody was coming for us, we knew we weren't going to die in a life raft," Farwell said.

Brazil's navy said the distress signal was first picked up about 5 p.m. Thursday, and an air force plane later the spotted rafts. Passing merchant ships plucked the castaways from the water, and by Saturday afternoon they were all back on land in Rio de Janeiro.

The first to dock looked disheveled and teary-eyed, wearing navy caps and clothing borrowed from their rescuers. They smiled brightly at times, but also broke down and cried as they spoke to reporters on the navy frigate that brought them to port.

Curry said the Concordia's crew had begun preparing 24 hours in advance after getting a forecast of rough weather and high seas, but nothing unusual.

"Those conditions are not at all extreme. It's kind of just another day at sea," Curry said. "It was an extraordinary event - just bad luck to be in that tiny patch of ocean at that time."

While his young charges receive extensive sailing training as part of the study program, luck also had a hand in keeping everyone alive.

The storm hit in the early afternoon at a time when most of the students were studying in protected structures on deck - which made it easier for them to scramble to life rafts.

Two rafts got tangled in the rigging - but the ship's cook had rushed so quickly from her chores that she was still clutching a kitchen knife, which was used to slice through the ropes and free the rafts.

Curry also said the school that operates the ship outfitted it with twice as many life rafts as actually needed for 64 people, so there was plenty of room for everyone even though all the rafts on one side were under water.

The 188-foot Concordia was carrying 48 students plus the crew, according to Kate Knight, head of West Island College International of Lunenburg, Nova Scotia, which operates the Class Afloat program for students in the final two years of high school and the first year of college.

School officials said 42 of those aboard were from Canada. Knight said others hail from the United States, Australia, New Zealand, Mexico, Europe and the West Indies.

Nigel McCarthy, president and CEO of the school, said a London-based maritime agency would conduct an investigation to determine why it took so long for the emergency beacon to be heard.

"I'm concerned, I'm concerned," he told The Associated Press. "Obviously we don't know the reality of what's happened at every stage of this process, and we're just thankful to the Brazilian navy for having gone and got them."

Katherine Irwin, a 16-year-old from Calgary, Alberta, had mixed thoughts about how the shipwreck would affect her sailing future.

"This was only my 15th day at sea. It was definitely a shocker," she said, eyes welling with tears. "At first I was, like, I'm never going back into the ocean. But after thinking about the friendships I made in the raft, I definitely would do it again."

Touching solid land for the first time, Irwin jumped about with her friends and did a little dance on a naval pier, smiling and giggling.

She headed to a waiting bus, and as it pulled out Irwin and the others waved to the Brazilian sailors and shouted out their thanks.