Korean Diver Dies in Search for Navy Shipwreck Survivors

South Korea's president ordered a military alert Tuesday after the country's defense minister said a North Korean mine may have been to blame for the sinking of one of its warships.

A South Korean diver died today during a tense rescue operation to reach possible survivors trapped underwater in the ship that sank last Friday, officials said. Another diver who lost consciousness has been transferred to USNS Salvor, one of four U.S. Navy ships assisting in the search recovery.

These rescue efforts are underway near Baengnyeong Island, at the western tip of a disputed maritime border between South and North Korea, where a blast ripped a 1,200-ton South Korean ship apart during a patrol mission.

Rough waves and strong underwater currents are hampering expert divers from reaching the two parts of the sunken ship. Fifty-eight crew members, mostly at the front of the ship at the time, were saved but 46 are still unaccounted for.

On Monday divers did manage to reach the back part of the wrecked ship where most of the missing soldiers were positioned at the time of the blast. Aware that the crew would have only enough oxygen in their watertight cabins to last until Monday evening, divers pumped oxygen into the ship through cracks in the stern, Rear Adm. Lee Ki-sik of South Korea's Joint Chiefs of Staff said.

They were diving in extremely difficult conditions. Strong currents churning up dust meant that they were only able to see less than a foot ahead even with a flashlight. The maximum time divers can stay underwater at 160 feet below is only eight minutes per dive.

"There was no response when our military divers knocked on the hull of the ship's rear," said Lee.

President Lee flew to wreckage site Tuesday to review search operations, meet with marines and console family members, the presidential Blue House said in a statement.

Lee told officers South Korea must maintain its military readiness until North Korea gives up its nuclear weapons program.

"When we are strong, we can defend ourselves. If we are weak, we'll face more danger," Lee said. "South Korea's military should be strong."

Four U.S. Navy ships that happened to be in the area to participate in the Foal Eagle Exercise, a joint bilateral annual military training, were quickly deployed to the site last Saturday on the request of the South Korean government.

"We are there to support the Korean navy and will be there for as long as they need us with our mobile diving and salvage unit 1 embarked on the USNS Salvor," Lieutenant Anthony Falvo, deputy public affairs officer for the U.S. 7th Fleet, told ABC News.

A guided missile cruiser USS Shiloh and two destroyers, USS Curtis Wilbur and USS Lassen, are also assisting. "Our team and our divers were involved in salvage operation when the I-35W Mississippi River Bridge collapsed in Minneapolis in 2007. So we are perfectly suited for this kind of operation."

Hope for Survivors

Military experts had told reporters that the chances of finding survivors after 69 hours were extremely slim but the families of the 46 missing soldiers are clinging onto hope, growing more and more anxious and angry at the slow pace of rescue efforts.

"He is not dead. I have a strong feeling that he is there, waiting for help!" whispered one man whose nephew is missing. "We're just all extremely disappointed and annoyed because the government is not moving fast enough and not updating us on what is going on," he said in a low exhausted voice.

Another man, Joo Sang-Rok, who is praying for the return of his nephew Cho Ji-Hoon, told ABC News that most of his family is in torment, his sister especially desperate as she waits for news of her son. "He is a good son. He enrolled himself in the navy at a young age to help support his poor family," said Joo who had come with his family to a naval base in Pyeongtaek, south of Seoul.

The cause of the blast remains unknown. According to survivors, the ship sprang up about a foot with a loud bang, and then exploded splitting in half. Experts ruled out initial speculation that it could have been an internal engine explosion because the power aboard the ship could not have been strong enough to split it in half.

Some local media outlets have been reporting the possibility of a torpedo shot from a North Korean submarine. But the consensus among military analysts is this seems unlikely as the type of torpedo that the North Korean navy possesses could not have been used in waters only 82-feet deep. Their submarines would find it difficult to operate under normal conditions in such shallow water and near impossible in these severe currents.

The most likely scenario is that it was a floating or submarine water mine, but it is difficult to determine who planted them, when, and why. The South Korean government initially had been cautious about administering blame. But on Monday, Defense Minister Kim Tae-young told lawmakers that it could have been one of thousands of North Korean sea mines from the 1950-53 Korean War. Both North and South Korean naval forces planted water mines then but have since begun been cleaning them. Minister Kim denied any South Korean culpability saying, "There are no South Korean mines near the Yellow Sea."

The shipwreck is close to where three naval clashes occurred between the two Koreas in 1999, 2002, and 2009. Both countries, still technically at war since the Korean War ended without a peace treaty, are in dispute as North Korea does not recognize the sea border drawn up between the two countries by the United Nations

The Associated Press contributed to this report