The lake is about 50 kilometres east of Oatlands.

A 29-year-old man was retrieved from the water but his identity has not been released by police.

Details remained sketchy last night, however, police said the couple’s boat overturned some time early yesterday morning.

They had launched their boat about 7.30am.

Constable Suzanne Jaenke said police were unsure why the boat had capsized, and were unable to confirm whether drowning was the cause of death.

Constable Jaenke said determining the cause of death would be a matter for the coroner.

The teenager had swum to shore in the cold water from the dinghy before walking up to seven kilometres to raise the alarm with friends at a nearby campsite.

The group managed to launch a rescue boat before police arrived.

The boy received medical treatment at the scene.

Emergency services, including police units from Oatlands and Kempton, attended the lake after being alerted to the incident about 1.40pm.

The boy and the man were not related.

The lake is a popular fishing spot.