'You can only imagine the horror': 8 bodies found, 26 people missing after California boat fire

More than two dozen people remain missing after eight bodies were found in the water near a 75-foot commercial diving boat that caught fire early Monday morning off Santa Cruz Island, California, sending the crew diving overboard and kick-starting a desperate rescue effort, according to authorities.

The only known survivors of the Conception, a vessel designed for extended diving trips, were five crew members rescued by a good Samaritan pleasure craft called The Grape Escape, sitting nearby. There were 39 people on board the ship at the time of the accident. Twenty-six people remain unaccounted for.

"I could hear some voices, so I put on a pair of shorts, walked to the door, and I see this boat out there all on fire, totally engulfed," said Bob Hansen, who owns The Grape Escape. "Thirty foot flames, at least -- a 75-foot boat and it was on fire from one end to the other. It looked like it had port holes down below deck and you could see fire through the holes."

"You can only imagine the horror," he added.

Four bodies have been recovered, while four others have been located on the sea floor, according to Santa Barbara County Sheriff Bill Brown. Two adult men and two adult women were recovered. They do not have identities of those bodies that were recovered and some may take DNA analysis to confirm.

The instability of the boat, lying upside down on the bottom of the water, is making further recovery difficult, the sheriff said.

Ventura County officials "fear numerous fatalities" as rescue operations continue, public information officer Bill Nash told ABC News.

Crew members said that three groups celebrating birthdays -- including that of a 17-year-old -- were aboard the vessel.

Capt. Monica Rochester, U.S. Coast Guard Los Angeles Long Beach Sector Commander, said the crew members were awake at the time of the fire and jumped off of the boat into the water.

"One of the fellows had a broken leg; he was in extreme pain," Hansen said.

The Coast Guard said it will continue to search for survivors through the night, but were prepared for the worst outcome.

Nash said officials are hoping people went over the side of the boat and made it to Santa Cruz. However, the fire happened overnight in pitch black, and the sleeping quarters were below deck. Nash said they "greatly fear loss of life here."

Santa Barbara County, responding to reports from the Associated Press, confirmed in a tweet late Monday night that more bodies have been found but that there would be no new information until Tuesday morning.

Emergency calls showed the desperation of those on board.

"I can't breathe," one passenger aboard the boat engulfed in flames near Santa Cruz Island said while making a mayday call.

Crews from the Coast Guard, Santa Barbara Fire Department, Ventura County Fire Department and Vessel Assist responded to a mayday call that was heard at about 3:15 a.m.

"The fire department crews were fighting the fire when the vessel sank 20 yards off shore in 64 feet of water," according to a statement from the Coast Guard.

"The vessel was reported as being on fire," the Los Angeles office of the U.S. Coast Guard tweeted earlier Monday. They added that "a group of crew members has been rescued (one with minor injuries) and efforts continue to evacuate the remaining passengers."

Rochester said the vessel was in "full compliance."

The cause of the fire is still under investigation, but said there was no reason to suspect criminality.

"We are working deliberately with the vessel owner/operator, who is with us at the time working on a plan to conduct further assistance for his vessel," she said.

The Ventura County Fire Department public information officers said in a tweet that their department responded to the fire at about 3:30 a.m. They said the Coast Guard is "helping support rescue operations for people aboard a dive boat."

The boat was drifting toward Santa Cruz Island, per the Santa Barbara Fire Department, and it was anchored when the fire started to burn. It currently has a portion of the bow sticking out of the water, per the Coast Guard.

The three-day trip launched on Aug. 31 and was expected back Monday morning.

A 16 member go-team from the National Transportation Safety Board will be traveling to the site, along with board member Jennifer Homendy.

Some investigators will leave Washington, D.C., late Monday, arriving in California sometime around 1 a.m. local time at the latest. The rest will leave early Tuesday morning.

ABC News' Kayna Whitworth and Mina Kaji contributed to this report.