There are many entrance exam for Indian Navy.  It depends on your qualification. The Exams you can apply:

NDA- Students studying in 12th can appear in this exam. this exam is conducted by UPSC. Once you clear the exams you will be called for SSB interview. To check the complete information you can go through with given below link.

NDA

CDSE- Students in final year of their graduation can apply.This exam is also conducted by UPSC. To check the complete information you can go through with  given below link.

CDSE

Good Luck!