The doomed diving boat that caught fire and sank early Monday off the coast of Southern California had been chartered by a local adventure company owned by a marine biologist — who is among the missing and feared dead.

“Please pray for my sister Kristy!” wrote Brett Harmeling, brother of Kristy Finstad, on Facebook.

“She was leading a dive trip on this boat,” he said.

Finstad co-owns the Worldwide Diving Adventures company, which chartered the 75-foot vessel — dubbed the Conception — through Truth Aquatics, a Santa Barbara-based boating operation.

Worldwide Diving was reportedly founded in 1972 by Finstad’s father, Bill Finstad, and later passed down to her upon his retirement. She and her husband, Dan Chua, run the business and lead excursions as licensed scuba instructors.

Chua is leading a dive trip off Costa Rica, according to Finstad’s brother, who was supposed to be with her on the Conception during the Labor Day Weekend getaway.

“I was going to be on this trip,” he told a Facebook user.

Attempts to reach Harmeling were unsuccessful on Monday night. Friends and families were sending their condolences to him after authorities announced that almost everyone on board the Conception when the fire broke out was missing and feared dead.

“We are praying and loving your family through all of this,” said one person. To which Harmeling replied, “Thank you.”

Finstad is described on the Worldwide Diving site as “a NAUI instructor with a degree in Aquatic Biology and a spirit of adventure.”

“There’s nothing better than seeing divers’ dream vacations come true,” she’s quoted as saying. “My mission is to inspire appreciation for our underwater world. I feel incredibly fortunate to be in the service of helping people invest in experiences of a lifetime.”

Authorities had recovered at least four bodies as of 4:30 p.m. local time Monday — and located another four on the bottom of the ocean floor, according to officials.

Thirty-nine people were said to have been aboard the ship.

Five members of the crew were rescued after the incident was first reported. The remaining 26 people who have been unaccounted for are feared dead, with local police suspecting that their remains are still trapped inside the Conception.

“We will search all the way through the night, into the morning,” said Capt. Monica Rochester, a Coast Guard spokeswoman, at a press conference. “But we should all be prepared to move into the worst outcome.”