Rescued students arriving in Rio

After clinging to life rafts in high seas for up to 40 hours, 64 students and crew, including a New Zealand teen, rescued from a sinking Canadian sailing ship have begun arriving in Rio de Janeiro.

The three-masted SV Concordia was on a five-month voyage that allows students in grades 11 and 12 and the first year of college to study while sailing around the world.

The ship's captain told The Associated Press that the vessel sank on Wednesday afternoon - a day earlier than previously reported. All 64 people aboard were rescued by merchant ships early Friday.

Captain William Curry said the Concordia's crew had prepared a day beforehand for what they anticipated would be rough but not unusual weather.

He was below deck when the ship suddenly keeled - which was normal. But it immediately keeled a second time, and Curry said he knew instantly the vessel was in great danger.

The captain blamed the wreck on a "microburst," a sudden, vertical downdraft; when the vessel keeled, the entire surface area of the sails was exposed to the powerful wind, and within 15 seconds, the boat went from sailing normally, upright, to lying on its side and beginning to sink.

Thirty minutes later it was completely underwater, Curry said.

Curry said that the Concordia's radio equipment was underwater and unusable, keeping the crew from being able to call for help, but an emergency beacon was automatically released into the water.

They abandoned ship and took to the rafts in high winds and heavy seas, spending more than a day adrift in the Atlantic before spotting the first signs of rescuers.

"We had been in the life raft for about 30 hours when we saw a search plane for the first time," Unsworth added. "That's when we knew we were not alone and that help was on the way."

The navy said the distress signal was picked up about 5pm on Thursday, and an air force plane later spotted life rafts in the ocean about 500km from Rio. Disheveled and teary-eyed, and wearing navy caps and clothing borrowed from their rescuers, at least 12 of the rescued docked in Rio at 10:45 a.m. on a Brazilian navy ship.

The rest were to arrive later in the afternoon on two merchant vessels. About 10 students stood on deck taking photos of themselves and the dozens of photographers waiting to meet them.

Auckland 17-year-old May Barry was among the rescued students.

Ms Barry, formerly from Long Bay College in the North Shore, had never sailed before and was scared prior to the trip.