Four rescued after boat sinks in Melbourne

Four people spent hours clinging to channel markers after their boat sank in Melbourne's Port Phillip Bay.

Their plight only became known when a pilot from harbour control was directing a container ship into the Point Richards channel near Geelong about 5am (AEDT) on Saturday.

He thought he heard a call for help, police said.

Unable to stop at the time, he raised the alarm, and water police and air wing began a search.

A man and two women were found clinging to one channel marker and another man was found clinging to another marker in a shipping lane.

It is believed the group had been there for about three hours after their boat sank.

A 40-year-old Norlane man, a 46-year-old Leopold man, a 50-year-old St Albans woman and a 46-year-old Belmont woman were taken to the Clifton Springs boat ramp where they were checked by paramedics.