The USS Watertown is supposed to be a Los Angeles-class attack submarine. However the submarine being shown as the Watertown is not always the same one, some of the shots of the submarine while surfaced are of a Los Angeles-class, but the shots of the submarine while submerged are of the much larger Ohio-class ballistic missile submarine, which has wide flat dorsal section, compared to the Los Angeles-class rounded dorsal section.
While Harm converses privately with the XO in the wardroom, Harm flops down in the captain's chair, at the head of the table. Nobody but the skipper sits in the captain's chair. In the real world of the US Navy, the XO would have politely asked Harm to take another seat.
During several underway scenes aboard the submarine, the skipper and others repeatedly use the order "all engines ahead full". The correct order is " All Ahead Full."
During one scene, while changing depth, already submerged, from a more shallow depth to 400 feet, the establishment footage shows a submarine on the surface and starting to make a dive -- that is, starting to submerge.
Aboard the submerged submarine the background sounds repeatedly include a deep metallic groaning. That's not authentic. That does not happen aboard a US submarine; that's a Hollywood invention.
The submarine in this episode was the USS Waterton SSN 696 according to the ball caps that were worn by the crew. However the USNS Watertown was actually a Missile Range Instrumentation Ship circa 1960. Submarnie SSN 696 is the USS New York. Which is still a Los Angeles-class submarine as described by Adm. A.J. Chegwidden
Harm keeps addressing the CO of the Watertown by his rank, "Commander". However naval tradition, and US Navy regulations, state that the commanding officer of a ship is to be addressed as "Captain", regardless of the rank they hold. This is not a mistake a Naval officer would make, to do so would be seen as being disrespectful. The only time Commander Flagler would be addressed by his rank would be when he is being spoken to by a senior officer, or while off-ship. But when he is carrying out his duties as the CO he is to be addressed as "Captain".