Into the Depths Once Again is actually a prequel to the first part of Wildgoose's Submariner Series that provides much needed background information on how Daria and Jane became career Navy officers. Beyond the brief look at them in The Last Journey Home, this was the first story to truly introduce Daria's family, including:
- Her husband, Trent, whom she finally got to know in the Lane fallout shelter where the Lane's and Morgendorffer's stayed after the nuclear exchange caused by the Y2K bug.
- Their non-identical twins, Amy and Jane.
- Jane's son by Jesse (who died in Washington D.C. during the war), William.
This information is introduced through interludes of the overlying story of Daria and Jane called back to duty early after a refit of their ship, the USS Cynical.