Hong Kong (CNN) The captain of a Hong Kong passenger ferry has been sentenced to eight years in jail for his role in a fatal collision that left 39 people dead in 2012 - the city's worst maritime disaster in four decades.

Lai Sai-ming was sentenced at the city's High Court on Monday.

A jury on Saturday had found him guilty of 39 counts of manslaughter and endangering the lives of others at sea.

Chow Chi-wai, the captain of the other vessel, which was owned by the Hong Kong Electric Company and had been carrying company employees and their families to watch a scheduled fireworks display, was sentenced to nine months in jail.

He was found guilty of endangering lives, but not manslaughter.

'Way below standard'

In sentencing, judge Brian Keith said that Lai's actions were not minor errors of judgment or momentary lapses of distraction but "fell way below the standard of professionalism" required in Hong Kong's busy waters.

Lai failed to keep a proper lookout and take any effective steps to avoid a collision, according to court documents. The judge agreed with the prosecutor's view that Lai didn't see the other vessel before the crash.

In mitigation, the judge noted that both captains had suffered from post traumatic stress disorder and were haunted by what happened that night, but said "it cannot be compared to what was suffered by those who lost their families in the tragedy."

Thirty nine people, including eight children, were killed after the two vessels collided near Lamma Island, on October 1, 2012.

Survivors described how the collision upended one of the vessels, flinging passengers into the water. Rescuers picked up 123 survivors but at least 92 passengers were injured in the incident.

Passengers on board the ferries said how they had only moments to escape.

Busy sea lanes

The narrow sea lanes leading into Hong Kong's main deepwater harbor are some of the busiest in Asia, with giant commercial freighters, ocean liners, passenger ferries and private boats of all sizes sharing the water.

Hong Kong is home to more than 200 outlying Islands, including Lamma.

The collision was Hong Kong's most lethal maritime accident since 1971, when 88 people died after the ferry Fat Shan capsized between Hong Kong and Macau during a typhoon.