Six people were missing after two boats collided in waters off Hong Kong late Thursday.
The accident comes after maritime safety fears were exposed when a ferry collision claimed 39 lives in October last year, in the city's worst boat disaster in decades.
A government spokeswoman said the fire department received a report at 7.54 pm (1154 GMT) that two vessels had collided off Stanley, located on the south-east of Hong Kong Island, and one had sunk.
Five people were pulled from the water and two were taken to hospital for treatment, while the hunt for the six missing remained underway more than three hours after the collision.
"We are still searching for the six, we don't know whether they are dead or alive," a government spokeswoman told AFP.
It was not immediately clear what caused the collision or what type of vessels were involved.
The government spokeswoman added that an investigation into the accident was underway.
The city's worst maritime catastrophe in 40 years last October saw a high-speed passenger ferry collide with a pleasure boat carrying around 120 people to watch national day fireworks.
The captains of the boats involved were last week each charged with 39 counts of manslaughter and face life in prison if convicted.
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.