 FACT: At many points through the film, Caseys rank is referred to  by different titles. He holds the rank of Chief Petty Officer. Early  in the film, Ensign Taylor refers to him as "Petty Officer",  something an officer would never do, even as a sign of disrespect.  Commander Krill refers to him as "Mr. Ryback", a title usually  reserved for junior officers. Many junior sailors refer to him by  his first name, unlikely, although not absolutely so, considering he  comes from the SEAL community. Most everyone should call him  "Chief".