In the bar scene, CDR Blackburn's dress blue uniform has the special warfare technician insignia above his rank insignia. This device is only used for warrant officers. SEAL commissioned officers are all line officers, who would have a gold star on their sleeves above the rank insignia.
When the female Ensign is called to talk to the captain, the captain calls he a Lt. As a butter bar she is an ensign and is not considered a Lt JG until obtains the rank insignia of a silver bar.