The USS Lansing and USS Mako used in this movie are fictional names. There have never been US submarines with these names. SSN 795 is also fictional.
The actual pictures in the Captain's room are of Casper Van Dien's wife Catherine Oxenberg and three of their children: India, Cappy and Gracie.
GPO3 with a gold chevron; Gold indicates 12 years of continuous honorable service. The young lad would need to be at least 30 to have that (very rare for PO3 to attain due to high year tenure) but he barely looks 20.