Hello Aspirant,

The eligibility criteria to join Indian Navy is you must have atleast 50% marks in your 10th class and 50% marks in your Physics, Chemistry and Mathematics subjects of your 12th class.

And as far as the NDA entrance exam is concerned, you just have to clear it and the main selection process is your SSB that will include group discussions, personal interviews and more . If you clear the SSB round, there will be a medical round only after clearing that, you can expect your name on the final list.

check these links, might be a help to you:

https://competition.careers360.com/articles/nda-eligibility-criteria

https://competition.careers360.com/exams/nda

All the best!