Differentiating Factors
Strength of your profile can be very well measured when we compare you to your applicant pool. For example if I compare you with another merchant navy professional, what do you think are the 3 differentiating factors? Is it that you have extensively worked on process improvements during dry dock projects or onboard ship? Or does your strength lie into your general management skills? Can you quick stint and promotions with TATAs a strong point? No easy answers here, start thinking on these lines.
Leadership
In your current role did you drive projects on your own? Did you motivate a de-motivated team? Did you face a crises situation? Did you take initiative and did good work for client? These are the examples you would have to weave in your essays. If you have such example to put in, believe me you stand in good stead not only for ISB but for US B-schools as well.
Goal Clarity
You have not stated your goals here. Do you wish to stay in Shipping/logistics/operations industry? Or do you wish to test the waters in a different industry? In a world where 1000s of applicants are applying to B-schools every year, an applicant's goal clarity is of paramount importance. What are your long term goals and in line with these what are your post-MBA short term goals?
Have you given a sincere thought to these questions? If not you should because they would be a part of your MBA essays/interviews for sure.
GMAT
670 is little low as a GMAT score, but there is no GMAT cut-off as such put by B-schools. Higher the better is the general thumb rule. Asian applicants esp Indians tend to have high GMAT scores. You can get an idea about B-school's GMAT expectations by looking at class profile of last year's admits, where in they give Average GMAT score for last year's intakes. For ISB this number is around 710.
Hobbies/Extra Curricular
If you do have decent achievements in Extra Curricular then do mention them in your essay in terms of what people or processes you have affected and what impact have you achieved?
