By this time, his friends' attention had been turned to another member of the group who was also fighting to stay afloat.

On Thursday, State Coroner Victor Yeo returned a verdict of misadventure into the death of Tay Demin who drowned in the sea off Siloso Beach on June 25.

The 17-year-old was waiting for his National Service enlistment at the time.

According to a toxicology report submitted to the court, Tay's blood and urine contained the drug ketamine.

Investigations could not establish how ketamine came to be in his system as he was not known to be a drug abuser, the court heard.

State Coroner Yeo said: 'It is very likely that the currents in the sea were too strong as Liang Xiang had encountered.'

'However, one cannot exclude that the presence of ketamine could have caused a loss of consciouness, confusion and disorientation.'

The court heard the group of seven teenage friends had gone into the water for a swim after arriving at the beach at 1.30pm.

Not long after, Tay was seen floating in the water about 10 metres from the shore and was told off by a friend who thought he was pretending to drown.

Moments later, Lim Liang Xiang, 19, who had swum away from the main group ran into trouble and struggled to stay afloat.

When he shouted for help, the attention of the group was diverted. A duty lifeguard heard Lim's cries, dived in and managed to rescue him.

However, when the group returned to shore, Tay, who was known to be a good swimmer, was no where to be found.

No one had heard him shout for help or saw him struggle in the water.

A frantic search was mounted by the group and two lifeguards on duty. It took about 20 minutes before a lifeguard, who was wearing a diving mask, spotted Tay's lifeless body on the seabed near where he was last seen.

He was in two-metre deep water at the time.

He was immediately pulled to shore but could not be revived. He was taken to the Singapore General Hospital where he was later pronounced dead.