A federal judge on Thursday sentenced a scuba dive boat captain to four years in custody and three years supervised release for criminal negligence after 34 people died in a fire aboard the vessel.

The September 2 2019 blaze was the deadliest maritime disaster in recent US history, and prompted changes to maritime regulations, congressional reform and several ongoing lawsuits.

Captain Jerry Boylan was found guilty of one count of misconduct or neglect of ship officer last year.

The charge is a pre-Civil War statute colloquially known as seaman’s manslaughter. It was designed to hold steamboat captains and crew responsible for maritime disasters.

Fatal Boat Fire California
Captain Jerry Boylan was the first to jump overboard when the ship Conception caught fire (AP Photo/Damian Dovarganes, File)

Boylan’s appeal is ongoing. He faced up to 10 years behind bars.

The defence had asked the judge to sentence Boylan to a five-year probationary sentence, with three years to be served under house arrest.

“While the loss of life here is staggering, there can be no dispute that Mr Boylan did not intend for anyone to die,” his lawyers wrote in a sentencing memo.

“Indeed, Mr Boylan lives with significant grief, remorse, and trauma as a result of the deaths of his passengers and crew.”

The Conception was anchored off Santa Cruz Island, 25 miles south of Santa Barbara, when it caught fire before dawn on the final day of a three-day excursion, sinking less than 30 metres from shore.

Thirty-three passengers and a crew member died, trapped in a bunkroom below deck.

Among the dead were a deckhand, who had landed her dream job; an environmental scientist who conducted research in Antarctica; a globe-trotting couple; a Singaporean data scientist; and a family of three sisters, their father and his wife.

Boylan was the first to abandon ship and jump overboard. Four crew members who joined him also survived.

Thursday’s sentencing was the final step in a fraught prosecution that has lasted nearly five years and repeatedly frustrated the victims’ families.

A grand jury in 2020 initially indicted Boylan on 34 counts of seaman’s manslaughter, meaning he could have faced a total of 340 years behind bars.

Boylan’s lawyers argued the deaths were the result of a single incident and not separate crimes, so prosecutors got a superseding indictment charging Boylan with only one count.

With the conclusion of the criminal case, attention now turns to several ongoing lawsuits.