Police were alerted at about 12.45am after a group of friends returned to shore near the northern end of Sai Kung peninsula and realised the man, identified only by the surname Chan, was missing.

The group, which included three other men and two women, had gone snorkelling at around 10pm the night before.

Police and the Fire Services Department deployed rescue teams for a surface sweep of the area, and divers from the force carried out an underwater search.

The group had been staying at the Jockey Club Siu Tong Camp.

Lai Chi Chong forms part of the Hong Kong Unesco Global Geopark, which attracts visitors and campers because of the rare volcanic rock formations along the shoreline.

Li Kin-kwong, the founder of the Hong Kong Institute of Scuba Training, said snorkelling was generally considered safe, but was dangerous at night because of low visibility and variable currents.

He explained that people in the water could easily lose contact with others when it was dark because of problems communicating with hand signals at night.

They also faced the risk of being caught up in, or separated, by currents, which could prevent them from swimming back to the shore.

“Most accidents happen when people are inexperienced and underestimate the environmental situation,” Li warned the public.

“You have to make sure you can swim well, have received sufficient training, and brought the right equipment before you go snorkelling or diving, and you should never go alone or at night.”

He added that the group might have been diving for crabs and fish because the spot had no coral reefs to beware of.

It was the second diving accident in just three days.

A 55-year-old scuba diver was found dead in the waters of Fung Wong Wat in Tai Po last Friday. He had gone diving alone the night before.

Another man, 58, man died after going snorkelling with friends in Sai Kung’s Ung Kong Chau last October.