The ferry was carrying passengers from the Gateway of India – a colonial-era monument on the waterfront that is symbolic of Mumbai – to the popular tourist spot of Elephanta Island, famous for its rock carvings.
“A Navy craft undergoing engine trials lost control and collided with a passenger ferry,” India’s navy said in a statement, adding that it regretted the “tragic loss” of lives.
The navy said there had been an “engine malfunction”.
The 13 dead included one naval service member and two representatives of an equipment manufacturer taking part in the tests, the navy said.
Two people seriously injured were taken to the naval hospital.
“Search and rescue efforts were immediately launched,” the navy said, with four naval helicopters flying overhead, while 11 naval craft and four coastguard or police boats searched the waters.
-Agence France-Presse