To become Navy officer you have to clear CDS exam conducted by UPSC. This exam happens twice a year (June and December). Here officer gets appointed as a permanently commissioned (PC) officer or as a  Short Service Commission (SSC) officer.

Permanently commissioned (PC) officer means till retirement

Short Service Commission (SSC) officer means officer for 10yrs and can be extended to 14yrs and also have the option for permanent commission.

Eligibility - 1) 12th passed or equivalent with science or mathematics (60%)

2) B.sc passed with 60%

3) BE or B.tech with 65% from recognized AICTE

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