Marine police launches and fireboats went to the area and, about an hour after the call, Cheung was found floating about 50 metres from the waterfront. He was taken to Tseung Kwan O Hospital, where he was declared dead at 1.45am.

A police officer said Cheung was a licensed diver and it was not the first time he had gone diving in the area with friends. He said there were no suspicious circumstances and that an autopsy would be carried out.

Hong Kong Underwater Association director Curly Wong Fan-tai said the area where Cheung lost his life was unsuitable for recreational diving. 'There are probably rubbish and miscellaneous items on the seabed. These pose dangers to divers,' he said. 'As there is a pier, boats will run in the area, which also poses danger.'

He said divers could go night diving after obtaining an advanced open water licence and should use sites recommended by the association.

International (Elite) Divers Training Centre course director Rommy Cheung Wai said a lot of divers liked night diving to catch shrimp and crabs and some might not follow the proper precautionary measures, such as diving with a buddy. 'Due to poor visibility, divers could face disorientation or buddy separation while night diving,' he said.

The association said divers should receive proper training in night diving and arrange a buddy system.