Question: what are coast guard ranks?
Answer: Ensign (ENS)(O1) Ensigns are generally inducted after Naval Officer training and obtaining a four-year degree. ... 
Lieutenant Junior Grade (LTJG)(O2) ... 
Lieutenant (LT)(O3) ... 
Lieutenant Commander (LCDR)(O4) ... 
Commander (CDR)(O5) ... 
Captain (CAPT)(O6) ... 
Rear Admiral Lower Half (DRML)(O7) ... 
Rear Admiral (RADM)(O8)