Two Hong Kong boat captains appeared in court Thursday accused of manslaughter over a ferry collision last year that claimed 39 lives in the city's worst maritime disaster in decades.

Chow Chi-wai, 56, and Lai Sai-ming, 55, were charged with 39 counts of manslaughter over the incident, which generated shock in the Asian financial hub, one of the world's busiest ports, that prides itself on its safety record.

The two defendants, who appeared calm, face life imprisonment if convicted. They have yet to enter their pleas after a prosecutor sought more time to put the case together, and were granted bail of HK$20,000 ($2,600).

The next hearing at the magistrates' court is scheduled for May 9.

The captains were arrested along with five crew soon after the October 1 crash between their two boats, with authorities pointing to human error as a possible cause of the accident.

Police said the remaining five, who have been out on police bail, would report back to the authorities later this month.

The city's worst sea catastrophe in 40 years saw the high-speed Sea Smooth collide with the Lamma IV which was carrying around 120 staff and families of power firm Hong Kong Electric to watch national day fireworks.

Hong Kong Electric is part of the business empire of Asia's richest man, Li Ka-shing. All of the dead and most of the 92 injured were aboard the party boat.

The Lamma IV's left rear was torn open in the impact, throwing scores of passengers into the sea. The vessel's stern was flooded within minutes, trapping people in the submerged cabin.

The Sea Smooth meanwhile limped the short distance to Lamma Island, a popular spot with expatriates, and disembarked its passengers as it was taking on water.

Fatal accidents are rare in Hong Kong, despite its crowded waters which often see high-speed hydrofoils vying for space with tourist junks, luxury yachts and a century-old public ferry system.

Chief executive Leung Chun-ying set up a commission in the same month to look into the crash. The commission is due to report its findings to the government later this month after over 100 witnesses testified at the inquiry.

The examination looked at the Lamma IV's structural soundness, why it began sinking so quickly, whether there was adequate safety equipment on board and whether the captain followed the rules of the sea.

Officials denied that the city's port reputation was damaged by the incident.

"This is definitely an isolated incident. The marine territory of Hong Kong is safe," Leung said at the time.