Umberto Garzarella, 37, and Greta Nedrotti, 25, died in the collision in the night between Saturday and Sunday.
Garzarella’s body was found on a small boat in the early hours of Sunday morning, while firefighter divers recovered Nedrotti’s body from the water of the popular lake later that evening, Italian media reports.
A search for Nedrotti was reportedly launched after women’s clothing was found on the boat near Garzarella’s body.
Witnesses said one of her legs was partially torn off and Garzarella had suffered a grave abdominal wound.
The Brescia prosecutor has ordered an autopsy on the bodies of the victims.
Two German men, aged 52, are under investigation for double manslaughter and failure to provide assistance, according to Italian news agency ANSA.
Italian newspaper Corriere della Sera reported that the men were located after other tourists noticed their docked motorboat was damaged.
Some locals also told the newspaper that the men were seen eating and drinking at a restaurant in Salò, the largest city on the west shore of Lake Garda.
The tourists underwent blood tests to establish whether they had been drinking before the incident.
They are not in custody, but while the inquiry is ongoing, they are not allowed to leave Italy and return to Germany.
Garzarella, who was the owner of a boiler maintenance company, had a passion for boating and owned the small vessel that was involved in the collision.
Nedrotti studied economics at university but was recently working as a hairdresser.
Italian police are conducting the investigation but did not reveal further details.
