MBA in Shipping and Port Management is a niche field of study. But this course is in high demand. If you are interested in the field, it doesn’t really matter that it is a specialized field. A graduate in Shipping and Port Management with decent skills makes almost double/triple of their equivalent MBA graduates. The reason for it is the less number of good Maritime professionals. 

IMU offers decent MBA courses. The Kolkata campus has a good faculty base. However, you shouldn’t entirely depend on the on-campus placement drive for employment. If you have the required skills, you can easily get placement opportunities.