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Hong Kong (CNN) -
The U.S. Navy submarine that collided with a submerged object in the South China Sea last weekend was operating in one of the world's toughest underwater environments, one filled with ship noise overhead and a seafloor with constantly changing contours that can surprise any crew, analysts say.
U.S. defense officials on Thursday did not provide details of the USS Connecticut accident, saying only that several sailors on board were injured when the submarine struck an object while operating submerged in the South China Sea.
The service said the injuries were minor and that the submarine arrived at the US naval base on the island of Guam on Friday under its own power.
A Navy spokesman told CNN that the front of the submarine was damaged and that a "full investigation and thorough evaluation" of the incident would be conducted.
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An advanced submarine
The Connecticut is one of three Seawolf-class submarines in the Navy's fleet, priced at about $ 3 billion each.
This 9,300-ton, 353-foot (107-meter) long submarine, commissioned in 1998, is powered by a single nuclear reactor and is manned by 140 sailors.
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Being larger than the newer Virginia-class attack submarines, the Connecticut can carry more weaponry than other US attack submarines, including up to 50 torpedoes and Tomahawk cruise missiles, according to a US Navy fact sheet.
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And despite being more than 20 years old, it is also technologically advanced, with updates to its systems carried out during its useful life.
The Navy says it is "exceptionally quiet, fast, well armed and equipped with advanced sensors."
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"These submarines have some of the most advanced submarine capabilities - in fact, the most advanced - in the industry," said Alessio Patalano, professor of warfare and strategy at King's College London.
How did you get into trouble in the South China Sea?
Although the Navy has not disclosed what the Connecticut collided with, analysts say conditions in the South China Sea may be a challenge for the submarine's sophisticated sensors.
"It could have been an object small enough not to be detected by sonars in a noisy environment," Patalano said.
According to the US National Oceanic and Atmospheric Administration, warships use what is called "passive sonar" to detect objects in the water around them.
Unlike "active sonar", which sends signals and records the time it takes for echoes to return to the ship, passive sonar only detects sound coming towards it.
This allows the submarine to remain silent and hidden from adversaries, but means that submarines must rely on other devices or multiple passive sonars to triangulate the location of an object in their path.
As the South China Sea is one of the world's busiest shipping lanes and fishing grounds, noises of all kinds from ships on the surface can mask what could pose a danger to the submarine below. according to analysts.
"Depending on where the incident occurred, noise interference (usually from overhead traffic) could have affected the sensors, or even the use that operators make of them," Patalano said.
Environmental noise, another possible problem
And it's not just maritime traffic that can pose problems for a submarine in the South China Sea, said Carl Schuster, a former US Navy captain and former director of operations for the Pacific Command Joint Intelligence Center.
"It is an area with a very poor acoustic environment," said Schuster, and even the very nature of the waters creates problems.
"Environmental noise from currents passing between the islands and inconsistent water conditions affect acoustic reception," he added.
It's also possible that something from below caused a problem, Schuster said.
"The environment around those waters and the seabed are in a slow but inexorable state of change," said Schuster.
"It is an area that requires constant mapping of the bottom contour. An unknown seamount can be found there."
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"That is why the countries of that region, the United States and China, constantly monitor and patrol them," added Schuster.
The accident was the second in which a submarine has been involved in the region this year.
In April, an Indonesian submersible sank in the Straits of Bali, killing all 53 crew members on board.
Indonesian Navy officials said the accident was caused by "a natural / environmental factor", but did not elaborate.
South China Sea Submarine