A rough measurement from the AH diagram puts the point of the deviation left/north at least 10000 feet (1.6 nm) offshore.
With an RVR of 2500 in smoke at VABB, and an easterly wind of 5-7 knots blowing that smoke out towards the sea, I'm not convinced the crew had anything in sight except water at the point they deviated north. Although I'll bow to those having experience with Mumbai's micro-weather patterns.