Thirty-four people are feared dead after an inferno ripped through a dive boat off the coast of Southern California, trapping dozens of passengers below deck in the dead of night, authorities said.

Twenty bodies have been recovered but 14 people are still missing and presumed dead, officials said Tuesday. The Coast Guard will seek to stabilize the scorched boat to recover some of the additional dead. Divers spotted several bodies on the ocean floor.

“It is never an easy decision to suspend search efforts,” Coast Guard Captain Monica Rochester said Monday.

Five of the six crew members, including the captain, survived.

The fire broke out on the 75-foot Conception, owned by Truth Aquatics, around 3 a.m. PST, while it was anchored overnight only about 20 yards off Platts Harbor on Santa Cruz Island, officials said.

Escape routes from the boat’s lower two decks were presumably blocked by fire, Santa Barbara County Sheriff Bill Brown said. No one from the third and second decks escaped, he added.

Among the presumed dead are students and parents from Pacific Collegiate School in Northern California, its principal said. “While this was not a school sponsored trip, our hearts and thoughts are with the families of the victims and those yet missing, particularly those of our students and parents on board,” the principal said in a statement.

Firefighters were still trying to douse the flames hours later when the vessel sank in 60-foot waters.

“ You can only imagine the tragedy. It’s horrendous. There are some things you can’t unsee ” — Bob Hansen, who rescued survivors of the dive boat fire

Crew members were awake and on the bridge when the flames began to consume the wooden-hulled vessel. Mayday calls captured the chaos at sea.

“I can't breathe,” one person on the ship reportedly said in a call, according to ABC News. CNN reported that a Coast Guard dispatcher was heard questioning a Conception crew member about firefighting equipment and an “escape hatch” for passengers during a mayday call.

“Can you get back on board and unlock the boat?... you don’t have any firefighting gear at all? No fire extinguishers or anything?” the dispatcher is heard asking. The crew member’s replies were reportedly inaudible.

The five crew members fled and were rescued by a pleasure boat moored nearby.

Bob Hansen, the owner of Grape Escape, told The Daily Beast that he and his wife were out on the water for the weekend, anchored in a cove on Santa Cruz Island, when they heard pounding.

“I put on some shorts and walk outside and open the door and here’s five guys in a little rubber boat and a 75-foot commercial boat on fire,” said Hansen, 73, from Madera, California. “It was really on fire... the whole thing engulfed in flames.

“The flames were shooting up 25 feet. I felt so helpless. It’s just burning. There were five tanks that were blowing up—or we thought there were—these big pops.”

Hansen brought the five crew members on board; one had a badly broken leg. He radioed the Coast Guard and waited for them to arrive, watching the scene unfold in horror, before ferrying the crew back to land.

“You can only imagine the tragedy. It’s horrendous,” Hansen said. “There are some things you can’t unsee.”

The Coast Guard struggled to put out the fire—which kept reigniting—before it burned the Conception down to the waterline. Then the flaming hulk sank, leaving its bow pointing out of the water.

“This is probably the worst case scenario you probably could have,” Brown said.

“To be in a remote location, to have a fire, to have minimal firefighting resources, and to have a fire that spreads quickly while most of the passengers are asleep—you can imagine how bad that is.”

The missing included one crew members. None of the passenger names were released, and authorities said the bodies that were retrieved would need to be identified through DNA.

The Conception came to rest at an unstable angle, complicating the recovery effort. “They’re waiting to find the right time to go in and recover those bodies,” Brown said.

Shayna Kreps, who lives in the Bay Area, told The Daily Beast one of her family members was on the trip. She said her family learned of the disaster on the news and had not been able to reach authorities.

“We're angry that we’re unable to get any information,” she said.

The cause of the blaze was unknown, but because it was a diving trip, there could have been air tanks on board exploding and reigniting the flames. The FBI was on the scene and the National Transportation Safety Board said it was sending a crew to the site.

The Coast Guard said the vessel was “in complete compliance” and that the owner was cooperating with the operation and investigation.

Truth Aquatics’ fleet is custom-designed for diving, according to its website, which says the company “caters to divers or ocean enthusiasts seeking a stress-free getaway.”

A calendar of events on the website indicated a three-day $665 Labor Day weekend trip was scheduled and being run by Worldwide Diving Adventures.

“Divers have the unique opportunity to explore the pinnacles of San Miguel Island,” World Diving wrote of the trip. “The beginning of September is the best time to be at San Mig, which see strong winds and swell during much of the year.”

Efforts to reach Truth Aquatics and Worldwide Diving were unsuccessful. But the founder of Truth Aquatics, who has been retired for years, was stunned by the tragedy.

“I spent 40 years running boats and we never had a fire... I'm just flabbergasted,” Roy Hauser told The Daily Beast, adding that he commissioned the Conception in 1980 and that it had undergone “tremendous remodeling” in the last three years.

Hauser wondered whether something electrical could have sparked the blaze given that it happened in the dead of night.

“The galley wouldn’t be open at that hour... The generator is running all the time. There’d be no cooking activity at 4 o’clock in the morning. The crew only starts getting everything ready at 5:30 in the morning.”