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About a week or so after the turtles first got mutated, the Kraang screwed up while trying to test their terraforming, and accidentally flooded Earth. For a while,t hey tested things to see if they could fix it, causing a flood of sea-adapted mutants, but eventually gave up and decided to leave for another planet. NYC is mostly underwater, with only a few buildings sticking up above. It looks something like this:


However, there a tons of boats, ziplines, docks, etc. connecting all of the buildings. It’s a big central hub for trading in whats left of civilized communities, with their main export being leftover artifacts from before the flood. Many people here are divers, and make a living trading off what they can scavenge from the depths. 

Because Splinter and the turtles were exposed to such a drastic change in their environment, the mutagen in the blood triggered to allow them to mutate somewhat further, giving them an advantage in the now flooded world. 

They live in the sewer system still, in one of the many pockets of air that remain down there, where the pressure is too great for humans to travel. Splinter rarely leaves the tunnels, instead, is practicing adapting ninjutsu to work underwater, and teaching his sons of what it was like before the flood.

The differences between the canon turtles and the Submerged turtles:

  • Clawed and webbed hands and feet
  • Sharp teeth for eating food raw, since there’s nowhere to cook things. They mostly eat fish, though they also eat octopus, crabs, mussels, jellyfish (sometimes), anything they trade with April/Casey, and whatever else they can hunt.
  • Slightly different markings.
  • Different straps and weapons. No mask.
  • Due to the density of water, swinging weapons don’t work well. Instead, the boys have different weapons, mainly used for hunting, but also attacking the miscellaneous mutant or bandit. They all carry at least two small knives on them, and ink bombs.
    -Donnie has a fishing spear 
    -Raph has serrated, barb-like daggers
    -Leo has short thrusting swords, not katanas
    -Mikey has a net, and usually more knives on him than his brother


  • Have their own, low-frequency language and mild echolocation. It only works when in the water, or if they’re touching on land. Generally only in their range of hearing.
  • Can hold their breath for approximately 3-5 hours when active, and days if they’re sleeping. 
  • Can drink saltwater. Like sea turtles, they cry to get rid of extra salt sometimes, not just when they’re sad.

  • April is still a Kraang hybrid in this AU, but doesn’t learn it until much later. Due to this, she isn’t effected by the bends, and can dive just as deep as the turtles can. He hair is cut extremely short to reduce maintenance.
  • Casey is a normal human and is best friends with April, and later, the turtles. He’s a dork and just braids his hair instead of cutting it off. Some days he regrets this.
  • The mutanimals are still here, albeit somewhat changed. Leatherhead is a saltwater crocodile mutant, Dr. Rockwell is an octopus mutant, Pete is a seagull mutant, and Slash is a leatherback sea turtle mutant.
  • Shredder died at sea approximately 13 years after the flood. 
  • Karai inherited his empire and all of his possessions. She found a journal hidden in a locked safe that contained her true heritage, but never searched for Hamato Yoshi, believing him to be dead. However, when she got into a skirmish in NY, she spilled mutagen on herself, and was turned into a Belcher’s Sea Snake mutant. She eventually befriended the turtles and discovered her father was Splinter.
  • Shinigami is Karai’s second in command and runs her empire while she’s away. Also her girlfriend.

Other random facts we’ll organize later

  • Fruits, vegetables, and basically any food other than seafood is very hard to come by and very expensive.
  • The turts use their diving prowess to trade stuff with their humans in exchange for interesting foods and things they can’t salvage themselves.
  • Theres lots of skeletons at the bottom because of the sheer number of people that died in the first flood.
  • Mikey is a little hoarder, and has a room full of random things like shells, animal parts, odd trinkets that he can’t trade, jewelry, and human skulls. Whoops.
  • Donnie collects mutagen canisters leftover from when the Kraang were here, because Splinter isn’t stupid in this AU and actually told his sons the story of how he foUGHT ALIEN ROBOTS so that nobody else gets mutated
  • There’s lots of random sea mutants roaming the world, but not all are hostile. 
  • There’s lots of pirates/bandits roaming the seas, and the boys have a habit of sinking/raiding bandit ships (both for goods and the pleasure of taking down ‘bad guys’. Mostly for the goods).
  • You bet your ass Karai is a kickass pirate snake empire leader. Also, apparently Belcher’s Sea Snakes are like… 100x more venomous than rattlesnakes or something. Need to do a bit more research. Fun :)