A naval helicopter, with four personnel on board, crashed off the Vishakhapatnam harbour on Tuesday.
Two crew members were immediately rescued while two others were missing and a search was underway for them, Navy officials said in New Delhi.
The Chetak helicopter crashed at around 15:00 hours during a routine training sortie, they said.
Navy has pressed into service its helicopters and ships to search for the missing personnel, they said.
The Navy has ordered a Board of Inquiry to investigate the reasons behind the crash of the light utility chopper, they said.
The Cheetah and Chetak choppers are the vintage of the 60s and the 70s and are the mainstay of the armed forces for ferrying small groups of personnel and light loads.
The Navy has already initiated the process for acquiring 56 new light choppers with twin-engines for replacing the vintage choppers.
The IAF and the Army are also in the process of replacing their fleet of such choppers.
In a similar crash in October last year in Panaji, three naval personnel including two pilots had died when their machine crashed at the Dabolim airport while landing there.
Before that incident, a Navy light helicopter crashed in 2005 when a chopper from Goa met with the accident near Belgaum in Karnataka on its way to Vishakhapatnam.