There are no options available online for admission to Merchant Navy after the bachelors. See if you want to be in merchant navy then you need to pass 10+2 with Physics, Chemistry and Mathematics with 50% marks at least. Apart from this you need to attend an entrance examination in order to get into merchant navy school. After that you need to do graduation under the discipline of your choice and eligibility. On passing the graduation you can be an Merchant navy. So you need to do the degree based on the merchant navy entrance.

To know more about Merchant Navy visit the link below:

https://www.careers360.com/careers/merchant-navy

I hope this answer helps. All the very best for your future endeavors!