Thirty-three people signed up to spend what promised to be a glorious Labor Day weekend aboard the Conception, a 75-foot boat that offered a scuba diver’s dream: unlimited diving among colorful underwater sea life, with gourmet meals served between dives.

But on the last part of the three-day trip, the ship caught fire off California’s Santa Cruz Island. At least 20 people died, Santa Barbara County Sheriff Bill Brown told The New York Times.

A day after Monday’s inferno, about 14 people are still missing.

“This is probably the worst-case scenario you can possibly have,” Brown said at a press conference. “You have a vessel that’s on the open sea, that is in the middle of the night. I mean, it’s 3:30 in the morning.”

Of the 39 people on board — 33 passengers and six crew members — only five people have been found alive. The five survivors are all crew members.

On Tuesday, search crews will make the grim transition from a rescue mission to a recovery operation.

Victims were likely asleep

Questions abound over why the boat caught fire, and whether lives could have been saved.

A mayday call reveals the tension between a Coast Guard dispatcher and the Conception’s captain. But only the dispatcher’s words could be heard.

The captain apparently reports a fire and provides a location. The dispatcher is heard saying, “And there’s 33 people on board the vessel that’s on fire, they can’t get off? … Roger, are they locked inside the boat? … Roger, can you get back on board and unlock the boat, unlock the door so they can get off? … Roger, you don’t have any firefighting gear at all? No fire extinguishers or anything?”

Later in the conversation, the dispatcher asks, “Was that all the crew that jumped off? … Roger, is the vessel fully engulfed right now … Roger, and there’s no escape hatch for any of the people on board?”

At one point, the caller says, “I can’t breathe.”

Ventura County firefighters were able to reach the boat within 15 minutes, the fire department said.

But by then, it was engulfed in flames.

Firefighters struggled to extinguish the fire because each time it was snuffed out, flames flared back up — perhaps because of the fuel on board, the Coast Guard’s Aaron Bemis said.

By 7:20 a.m., the ship began to sink in 64 feet of water. The boat had burned down to the water line, Santa Barbara County fire spokesman Mike Eliason said.

Many of the passengers were below deck, most likely sound asleep when the fire broke out, authorities said.

None of the people who were on board have been identified.

The company that operates the Conception, Truth Aquatics, declined to comment to CNN.

An agonizing wait

James Kohls waited anxiously to learn the fate of his brother, Mike Kohls, the galley cook and a deckhand on the Conception.

“It’s very surreal at the moment,” he told reporters. “They were going to let me know whether he was one of the survivors that got off.”

He said Mike Kohls, a lifelong surfer and father of a daughter, is typically making breakfast for the passengers on the ship around 4 a.m.

Eliason, the fire department spokesman, said it’s still possible some passengers may have survived. But the odds are stacked against them.

“We’re still holding hope that someone may have swum to shore,” Eliason said.

“When they anchor overnight, they’re pretty close to shore. We have to hope, but we plan for worst-case scenario.”