Emergency workers at the scene of a capsized ferry were finding bodies but not survivors Friday morning in an increasingly grim operation marred by confusion and complicated by strong currents.

A series of aborted and failed rescue attempts compounded the agony among family members awaiting news on a nearby island, as optimism dwindled in what is shaping up as one of South Korea’s worst peacetime disasters.

Since Thursday night, 16 bodies have been found floating in the water around the hull of the overturned vessel. And no survivors have been pulled from the ferry since Wednesday, despite more than 500 professional divers and scores of coast guard boats working in the area.

Earlier in the search operation, some relatives clung to hope as text messages purportedly from those still alive and trapped in the ferry popped up on South Korean online forums. But South Korean police now say those messages appear to be hoaxes. Police say they have checked cellphone records of missing passengers and determined that none have made calls or sent texts after the ferry sank, according to the Yonhap news agency.

Two days after the ferry capsized in the Yellow Sea off the Korean Peninsula’s southwestern coast, nearly 300 passengers remain unaccounted for. Fears are growing that the death toll, now at 25, could skyrocket.

South Korean officials said powerful currents and poor visibility were hampering the rescue in an area known for its bedeviling waters. Aerial footage showed the 6,835-ton Sewol almost entirely submerged in the water — only its blue bow was sticking out — as whitecaps washed over its hull.

One volunteer diver who had joined the search told MBN, a South Korean broadcasting network, that the rescue was badly disorganized and that authorities on site had not given scuba gear to divers or provided blueprints of the vessel.

Kang Byung-kyu, a minister for security and public administration, said during a news briefing that the currents and murky water posed “tremendous obstacles.” For part of the afternoon Thursday, the diving operation were put on hold. The divers have been attempting to pry into the ferry’s numerous corridors, but they did not manage to do so Thursday. Passengers’ relatives have been terrified about what such delays might mean.

“My kid is dying out there,” said Christine Kim, whose daughter is among the missing.

South Korean officials say 179 have been rescued — none since the day the ferry capsized — and 271 are missing. Seoul has provided conflicting figures at various points in the search while drawing growing criticism for its response.

Relatives of those on board gathered at a gymnasium in Jindo, an island off the southwestern coast of the Korean Peninsula, where they spread out on blankets, packed the bleachers and tried to deal with dread and uncertainty. Some were wailing Thursday, while others were furious. Some watched a large projector screen showing a TV news feed. A few, shocked and tired, were hooked up to intravenous drips as they lay on temporary beds.

When South Korea’s prime minister visited the gym just after midnight Thursday, he was sprayed with water. Another person tossed a shoe at him. Thursday afternoon, when South Korean President Park Geun-hye and another official held an impromptu meeting with the crowd, parents of the high-schoolers on board screamed that divers were not in the water trying to help.

Boats sink when something causes their density level to drop lower than that of the surrounding water. Here are four common ways that happens. (Kate M. Tobey and Gillian Brockell/The Washington Post)

“Time is running out,” one said.

“I am very much concerned that rescue efforts are slow even though so many personnel and equipment were mobilized,” Park was quoted by South Korean news media as saying during a Coast Guard tour of the rescue site.

Some of the initial criticism has been leveled at the ferry’s captain, Lee Joon-seok, who was one of the first to abandon the vessel. Another member of the crew, Oh Yong-seok, told the Associated Press on Thursday that the captain did not give evacuation orders to passengers when the ferry began to tilt perilously.

Instead, Lee instructed passengers to put on life vests and stay put. Only 30 minutes later did he give orders to abandon ship, but Oh said it was possible that the message was not relayed on the public address system.

Lee appeared in front of reporters Thursday wearing a hooded sweatshirt, which he closed tight to obscure his face. Lee said he was “deeply ashamed” for what had happened. South Korean news media reported that he was being interviewed by police.

Among the 475 on board, 325 were students from a high school in Ansan, just south of Seoul. The vessel departed from Incheon, a major port, and was bound for Jeju — a popular southern island — in what would have been a 13-hour, 30-minute journey. Survivors said the ferry was jolted by a loud noise when it was about three hours from its destination. It then began to tilt. Within two hours, it was upside down and submerged.

South Korean authorities have not indicated that there are signs of foul play, and some experts said that the ferry could have struck a rock or another object. According to Yonhap, a coast guard official said at a news briefing that the ferry “took a path slightly different” from the route recommended by the Maritime Affairs Ministry. Koh Myung-seok, the coast guard official, also said the vessel made a sharp turn where it was supposed to make a gradual one, possibly knocking some of its cargo out of place.

Those who are unaccounted for are thought to be trapped in the ship. Some at the gymnasium tried to make phone calls to their children, hoping for a sign of life.

The mother of one teenager on board said she received a call about 8:52 a.m. on the day of the accident from her daughter, Yoon Sol, who told her that the ship was shaking. The mother, who did not give her name, said she told her daughter to be calm and to listen to instructions.

“Sol was very excited about her school trip to Jeju. All I want is their safe return,” she said.

“I will wait here until I see my daughter, whether dead or alive,” Yoon’s father said. “I’ll take her body safely home.”

Harlan reported from Minamisanriku, Japan.