Two women who were on the speedboat, which was found on the beach, were later arrested. The body of a 39-year-old man with a heavily tattooed arm was in it.

The arrests and the find came after police received a call around 12.50am from a 24-year-old woman, who said her 42-year-old boyfriend was feared to have drowned after going missing while having a midnight swim at Lung Kwu Tan.

Rescuers then found the body in a seven-meter boat without a registration number on the beach.

Police later came upon the two women at Tuen Mun Town Plaza. One was the woman who called the police while the other, aged 36, had no identification documents.

The older woman was arrested for illegal entry.

A source said the 24-year-old has a recognizance form, which is a temporary identification document that allows her to stay in Hong Kong. She lives with the man who is missing in a public rental flat.

She told officers that she, her boyfriend and another couple went out to sea in the speedboat.

Her boyfriend and the man with the tattoo then decided to have a dip but got into trouble in the water.

Fire Services Department divers and a Government Flying Service helicopter conducted a search in the early hours of the morning.

Based on the police's preliminary investigation, the younger woman was arrested on suspicion of aiding and abetting others to land in Hong Kong unlawfully.

Police found two life vests and a black handbag on the beach that could be related to the case.

A source said the suspicion was that the speedboat was used to bring people into Hong Kong illegally, except that it hit a reef.

However, another source said that the speedboat was carrying the two couples out to sea for a night swim.

The speedboat made a sharp turn when a police vessel was spotted. This sharp turn caused the two men to be thrown overboard.

It was alleged that the one steering the boat abandoned it with the two women when they had a chance to get away.