Which is the best college for the Merchant Navy in Mumbai?

Well I do not agree with the question firstly.

You need to go to the best Merchant Navy Institute , it should not depend upon location at all . Your priority should be to get into best college ,have the best placement and then move ahead in life . Now if that college is in MUMBAI or Kolkata should not be a reason to change your mind.

Now coming to your point:

For DNS

1. AEMA , Karjat( Anglo Eastern Shipping Company)
2. Get sponsorship of Companies like Scorpio , Synergy , Wallem’s , V Ships ,Great Eastern.