SINGAPORE - The authorities have found the body of a 41-year-old man who went missing on Sunday (Dec 6) afternoon while snorkelling alone near Sisters' Islands Marine Park.

In an update on Tuesday night, police said they found and retrieved the body from the waters near Sisters' Island at around 5.45pm.

They had mounted a search and rescue operation on Sunday together with the Maritime and Port Authority of Singapore and the Singapore Civil Defence Force after receiving a call for help at about 12.40pm.

A park visitor who was on the island on Sunday told The Straits Times that the man's wife had approached him at about 12pm that day to ask if he had seen her husband.

The woman, who looked panicked and appeared to be in her 30s, described her husband as big-sized and said he had been missing for four hours, said the visitor, who wanted to be known only as Mr Ariff.

The 25-year-old goods vehicle driver said the woman told him that her husband had planned to snorkel for 30 minutes.

"We were shocked (at) how he's been missing for so long, but we had just arrived in the area," Mr Ariff told ST.

With his friends, he went into the water where the man was last seen snorkelling, but said it was very deep and the currents were too strong.

While they were swimming, they noticed police boats circling the area and officers walking around the island, presumably in search for the missing man, said Mr Ariff.

He left the island at about 4pm that day with his friends, saying it was raining heavily as he left.

The police are investigating the unnatural death.