Helicopters and divers scoured the waters off India's financial capital of Mumbai on Thursday in a search for survivors of a freak boat accident that killed at least 13 people a day earlier, three navy personnel among them, officials said. A naval speedboat lost control and collided with a privately owned vessel taking tourists to the nearby Elephanta caves, famed for their rock art. Navy and coast guard vessels joined in to search the harbour for at least two people still believed to be missing, an adult and a child, said a naval officer, who sought anonymity as he was not authorised to speak to the media.