(CNN) It was touted as a " warrior ," a 75-foot ship that gave ocean tourists speed, comfort and all the amenities they need.

The Conception was a hit with scuba divers and actor Rob Lowe , who said he had been on the California-based boat "many times."

But after 38 years at sea, the boat perished in a raging inferno on Labor Day, taking more than 20 lives with it.

A firefighters tries to extinguish the blaze that engulfed the Conception boat.

"This is probably the worst-case scenario you can possibly have," Santa Barbara County Sheriff Bill Brown said.

Here's what we know about the vessel and its last excursion:

Guests were on a 3-day, $665 trip

The 33 passengers on Conception's final journey were on a trip "designed by divers for divers," trip organizers said

"Night dives are delightful; octopi roam the reefs and bioluminescent zooplankton flash colors to silhouette the diver," an advertisement read.

The Conception launched in 1981 and could carry 46 passengers.

Passengers enjoyed custom-made gourmet meals, unlimited diving and "an opportunity to explore the pinnacles of San Miguel Island."

Organizers said Truth Aquatics, the company that operates the boat, is known for its professionalism.

"Their commitment to service shows through the smiles of crew members that love their jobs and undergo special safety training," the advertisement said.

Truth Aquatics, the company that operated the Conception, has declined CNN's requests for comment.

The passengers were not locked in the bottom deck

It's still not clear what caused the vessel to catch fire around 3:14 a.m. Monday, about 20 miles away from the coast of mainland California.

A mayday call between the boat's captain and a Coast Guard dispatcher suggested passengers may have been locked.

"There's 33 people on board the vessel that's on fire, they can't get off?" the dispatcher is heard asking. "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?"

But Coast Guard Capt. Monica Rochester said "there are no locked doors in accommodation spaces" where passengers slept on the Conception.

"The only privacy that you have ... are curtains," Rochester said Tuesday.

Footage from a 2018 video aboard the Conception shows beds separated by curtains.

She said chaos and confusion during the inferno may have led to misunderstanding about the passengers possibly being locked.

"A lot of activity was happening, as you can surmise, coming over the communication system ... lot of confusion," Rochester said.

Guests were trapped by fire

While passengers were not locked in the sleeping deck, they were apparently trapped by the blaze, Sheriff Brown said.

"There was a stairwell to get down the main entryway, up and down, and there was an escape hatch. And it would appear as though both of those were blocked by fire."

A layout of Conception's sleeping quarters shows only one stairwell leading up to the next deck.

The Conception passed its annual inspection

"This vessel is required to be inspected annually by the US Coast Guard, and it has been compliant," Rochester said.

The inspection requirements include smoke detectors on board, she said.

File footage from 2018 shows divers on board the Conception.

In addition to its safety features, the Conception was lauded for its size, speed and "perfectly tailored design," Truth Aquatics said.

"The larger size allows for a revised galley and bunk layout, including more double bunks, bathrooms, and showers," the company said.

"This makes the Conception ideal for larger charter groups or limited load trips, with enough comfort to easily bring the Southern Islands within reach."

A veteran of the boat narrowly escapes tragedy

Dale Sheckler, co-founder of California Diving News, has traveled on the Conception more than 100 times.

He was supposed to go on the ill-fated trip over Labor Day weekend. But a recent hip surgery may have saved his life.

"I just wasn't able to go out on the boat this particular weekend," Sheckler said.

"It was very painful to see this happen. I love the boat. I love the crew. I love the owners, they're just fantastic people."

He said the tragedy will have a lasting impact on the tight-knit diving community.

"It'll send ripples through the community for years to come, the amount of loss," Sheckler said. "It's just devastating. I just can't imagine, as the names come out, I know I'm going to be shocked when I see the names."