A man is dead after a sailing boat capsized near Kurnell in Sydney’s south Monday morning.

A woman raised the alarm with emergency services after swimming from the capsized vessel at Boat Harbour to shore at about 5am.

It sparked a search by police and ambulance crews, who discovered the body of a man near Wanda Beach.

He couldn’t be revived.

The woman was treated at the scene by NSW Ambulance paramedics and was taken to Sutherland Hospital for observation.

It’s unknown if those on board were wearing lifejackets.