(CNN) -- The search has been suspended for 17 crewmen missing at sea after the sinking of a Korean fishing vessel in the frigid ocean waters around Antarctica, a New Zealand rescue agency said Tuesday.
Twenty survivors and five dead were were recovered after the Korean-owned-and-operated No. 1 Insung sank Monday about 1,150 miles north of McMurdo Base, the Rescue Coordination Centre New Zealand said.
"Unfortunately the Southern Ocean is an extremely unforgiving environment," mission coordinator Dave Wilson said, referring to waters also known as the Antarctic Ocean.
Wilson said the extremely cold sea temperatures -- barely above freezing -- meant that survival times in the water "would be very short."
"We understand the vessel sank very quickly and the crew had to abandon ship without time to put on adequate emergency gear," he said. "Sadly, it is exceedingly unlikely that anyone not picked up yesterday could have survived."
Weather conditions, which were relatively mild at the beginning of the search, deteriorated Tuesday as a blizzard and fog moved in, Wilson said.
The ship sank about 6:30 a.m. (12:30 p.m. ET Sunday) in a remote swatch of the ocean some 1,850 km (1,150 miles) north of McMurdo, a U.S. research center on the tip of Ross Island. Maritime New Zealand learned of the incident around 1 p.m., some 4 1/2 hours later.
The 58-meter (190-foot) fishing trawler left on November 2 from South Korea to fish in Antarctic waters, said Ham Un-Shik, a spokesman with the Busan Coast Guard in South Korea. It had 11 Indonesians, 11 Vietnamese, eight Koreans, eight Chinese, three Filipinos and one Russian on board, he said.
There was no emergency radio call before the incident, and it is still not clear what happened, Henderson said.
CNN's Brian Walker contributed to this report.