hello aspirant,

it actually depends on you which course you want to persue, however both the courses are very good, for students who want to make a career in the computer applications, programming, and software development, for them, the BCA course in data science is better whereas , BSc in nautical science will be a  multidisciplinary subject (comprising of science , mathematics and physical training) that deals with techniques and knowledge involved in navigating and operating a ship safely from one point to another.

bsc in Nautical Science degree enables the graduates to become Navigating Officers on-board on merchant ships plying worldwide. Joining as a Deck Cadet after graduation, one needs to complete the training process

in my opinion, both the fields are completely different and it depends on you which course you want to take.

hope that helps