Twenty-two fishermen were presumed dead after their South Korean trawler sank suddenly off Antarctica on Monday, giving them no chance to don protection from the icy waters, rescuers said.
Maritime New Zealand said another trawler plucked 20 crew members from the sea shortly after the 'Number One Insung' sank but the rest of the 42-strong crew could only survive 10 minutes without proper immersion suits.
Five crew members died immediately when the boat went down about 6:30am (17:30 Sunday GMT), some 1,000 nautical miles north of the McMurdo Antarctic base and rescuers initially hoped some of the 17 missing had reached a lifeboat.
Maritime New Zealand coordinated desperate efforts by five trawlers in the area to find the missing men but admitted defeat late Monday that there was no chance they were alive.
"It (is) becoming increasingly unlikely further survivors (will) be found," rescue controller Dave Wilson said.
Maritime NZ spokesman Ross Henderson said the boat appeared to have gone down in calm conditions and did not send an SOS.
"We had no distress signal. At this stage we don't know what caused the vessel to sink," he told AFP.
"There was no emergency communication or beacon alert of any type, which we would normally expect in these sort of situations. We don't know what the reason for that is."
He said information received from the rescue vessel and the fishing company was that the trawler went down very quickly, and those who were able to abandon ship did so directly into the water without life jackets or immersion suits.
A coastguard spokesman in the southern South Korean port of Busan, where the ship is based, told AFP there were eight Koreans, eight Chinese, 11 Indonesians, 11 Vietnamese, three Filipinos and one Russian on board.
The nationalities of the dead are unknown.
Henderson said five fishing vessels -- two from South Korea and three from New Zealand -- initially assisted the search under direction from New Zealand authorities, who have responsibility for rescue missions in the area.
Plans to send a Royal New Zealand Air Force long-range Orion plane were scrapped because it would take at least eight hours to reach the location, Henderson said.
The 20 survivors and bodies were on another South Korean fishing vessel, Number 707 Hongjin.
Henderson said New Zealand's rescue coordination centre was not informed of the accident until 1:00pm, about six-and-a-half hours after it occurred.
The waters around Antarctica are notoriously rough but Henderson said conditions Monday consisted of light 10 knot winds and a one-metre (3.3-foot swell).
The trawler was fishing for Patagonian toothfish.
The fish, marketed as Chilean seabass, is popular in South America, the US and Japan and is often illegally fished and is on the Greenpeace red list of species in danger of being unsustainable.
Most toothfish are caught using bottom longlines and some by bottom trawling, Greenpeace says.
It said the fish, known as "white gold" in the industry for its highly valued flesh, lives in waters so cold that it has a type of anti-freeze in its blood.
The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR), the global body overseeing fishing in Antarctic waters, said the Number One Insung had a valid licence to fish in the region.