Factual error: As it says at the very end of the movie, the year is 1969. In the near ending when Carl is in his room getting ready to go to the court hearing, which re-inlists him into the navy, if you look out his bedroom window there's a flag with 48 stars. In 1969 the flag was already 50 stars.
Factual error: When Billy Sunday goes into Pappy's cabin, Pappy is shining some medals. As Pappy is giving his speech about things not mixing, one of the medals displayed is a Meritorious Service Medal. This medal was not introduced until 1969, long after this scene was supposed to have taken place.
Factual error: When the black scuba is out for his first (or second) weekend off school, he is at the port watching a ship passing. The prow of that vessel is "bulbous bow" type, (a kind of "appendix" in the prow that increases the speed). The "bulbous bow" concept for merchant marine vessels didn't start up until around 1964.