Dear Abhishek,.
Eligibility criteria for Merchant navy is depend on the course. Basically you should have 55% marks in 12th PCM an 50% marks in English. you should not have color blindness but 6/6 and +- 25 is permissible. There is no concern of height and health.
For more detail you can visit www.cruiselinefoundation.com

Merchant Navy professionals have options of working with government shipping companies as well as private companies. Besides they can work for Foreign shipping companies as well. Remunerations in all these sectors are very good. Besides there are many perks and one gets to visit many different countries. Also the entire salary is saved as there is no expenditure on the ship as all the basic facilities are provided free on the ship. BSc. Nautical Science is the course which has to be undertaken by the merchant navy aspirants. The course is conducted by government institutes as well as private institutes most of which provide employment with themselves to the students after they finish their course. The entrance to BSc. Nautical Science course is based on a written test and an interview.