Hey there

To join Indian Navy as a commissioned officer you need to clear exams namely either NDA or CDS. In NDA you need to be either in 12th or passed recently or you should have age limit for that. For CDS graduation is needed. Both exams are tough both in difficulty level of questions also the main ssb which is a process of rejection students say as number of students getting selected are very less as compared to what comes in ssb.

Check details of CDS

https://www.google.com/url?sa=t&source=web&rct=j&url=https://competition.careers360.com/exams/cds&ved=2ahUKEwis3P-V4qDlAhURi3AKHXeaC5wQFjABegQIAxAB&usg=AOvVaw2451DxpBD9qLOMNfnFWOjn

Check about NDA

https://www.google.com/url?sa=t&source=web&rct=j&url=https://competition.careers360.com/exams/nda&ved=2ahUKEwiXwuih4qDlAhVViHAKHfSmBvoQFjAAegQIAhAB&usg=AOvVaw2ltw_zRnHDyQSj0PmzlrIA

Good luck