Three people found unconscious on boat

Two men and a woman have been rushed to hospital after Water Police found them unconscious on a boat circling out of control in Victoria's Port Phillip Bay.

Officers were alerted at around 8.15pm on Tuesday and with the assistance of the Airwing found the boat about 500 metres off St Leonard's boat ramp east of Geelong.

When they boarded the vessel they found two men and a woman unconscious, prompting the Airwing to fly paramedics to the scene.

A 60-year-old man was airlifted to The Alfred Hospital in Melbourne while the two others were taken by road ambulance to Geelong Hospital.

Police say the exact circumstances leading to the incident remain unclear but it's believed a fault may have occurred on the boat, causing the trio to lose consciousness.

A marine surveyor will examine the boat on Wednesday.