A quick snippet from one of the side-plots, about a damaged submarine being chased out of the Yellow Sea by the Chinese navy! This series will blend post-apoc (realistic, not zombies) with military thriller! Coming early 2022!

“Depth six-fifty, Captain,” the pilot announced.
“Make your bearing zero-five-zero,” the CO replied with a little more composure.
“Zero-five-zero,” the pilot repeated.
“Sir, the transient is back,” one of the other sonar operators reported.
This is the first time we’ve been this deep since the damage, Darren realized. Water is under greater pressure, a little more saline dense, too... Maybe twelve is too fast…
“Contact!” the Chief sonar operator yelled. “Sierra Three, bearing two-twenty, range 1800 yards!”
“Depth?!” the CO demanded. While not always readily available information, the modern submarine force largely had a series of sonar arrays on each side of the boat. When they all picked up the same noise, the ship’s computer could use trigonometry based on the slightly different angle to provide a probable depth.
“Five-hundred feet, Conn! She’s back under the thermal.”
“She’s flooding tubes!” screeched the other sonar technician who was barely able to maintain her calm in the realization they were now engaged in combat. The flooding of torpedo tubes exposed weapons to salt water, creating extra work when they weren’t actually launched. There would be no other reason to do that except for its primary purpose of getting ready to shoot.
“All ahead full, right full rudder!” the skipper yelled. “Counter-measures to starboard on my command! Weapons, flood all port tubes!” Both the pilot and the weapons-and-counter-measures stations acknowledged their orders.
A common evasive tactic was to try to create a knuckle in the water by turning hard at a high rate of speed. Create turbulence in the water that would cause a torpedo to lose its track. That hasn’t worked for us against the Ruskies for nearly three decades, Darren thought. Then he remembered that China’s first nuclear subs were based on old Soviet designs. Maybe they’re still using outdated equipment.
“Outer doors opening!” the junior sonar operator yelled.
They’ll be shooting in a few seconds!
Then the dreaded words no submariner wanted to hear their sonar operators say… “Torpedoes in the water! Tracking two torpedoes, bearing two-three-zero, range 1500 yards, speed fifty-five knots!”