Sailing on-board INS Subhadra, a naval off shore patrol vessel and guarded by the elite Marine commandos, the President is reviewing a fleet of 81 ships and 44 aircraft as part of the 10th Presidential Fleet Review.
Donning a Navy cap, Patil sat on an elevated platform under a Navy emblem umbrella, created specially for the event on INS Subhadra.
The President is accompanied by defence minister A K Antony, the three service chiefs and four Cabinet ministers on-board the warship.
The review began at 0900 hours with a 150-men Guard of Honour and customary 21-gun salute accorded to Patil, the Supreme Commander of the Armed Forces.
Patil began the review by first sailing past the INS Agray- an anti-submarine patrol vessel- as the sailors took off their caps and hailed their Supreme Commander with the shouts of 'Rashtrapati ki Jai'.
Patil, in response, stood up and saluted each of the ships.
Following the review of its fleet, Navy will offer a brief glimpse of its air power by flying its fighter, transport and surveillance aircraft during the three-hour journey.
Patil had earlier created history by flying in a Sukhoi fighter jet and riding a battle tank of the Army.
To secure the sea for the event, Navy has turned Mumbai anchorage area and its western coast in a fortress by putting in place the highest level of security in recent times.
While 15 different naval and coast guard platforms have been deployed to guard the area, round-the-clock air surveillance is being done from INS Shikra.
Anti-missile batteries have been activated to tackle any threat and each participating ships in the review is being guarded by its own security detail.
Navy has also stopped all maritime traffic in the sea and Mumbai Police has put in place access control measures on roads leading to Mumbai dockyard for the event.