Well, it depends on the specific story. Some 'phantom submarine' tales might be based on real submarines that were involved in covert operations. For example, during the Cold War, both sides had submarines doing secretive patrols and surveillance. If one side detected an enemy sub briefly and then lost track of it, it could be called a 'phantom submarine'. So in the context of a true story, it might be a real military sub.
A really cool submarine book is 'Voyage to the Bottom of the Sea' by Irwin Allen. It has a lot of exciting adventures and scientific exploration as the crew of the submarine Seaview faces various threats and mysteries. It combines action, science, and adventure very well.
It could be a lost or abandoned submarine. Maybe it was part of a military experiment that went wrong, and it's now drifting around, appearing and disappearing like a phantom.
In the traditional TMNT universe, male turtles like Leo getting pregnant goes against the biological norms of the franchise. However, in fanfiction, anything can be reimagined. Some fanfiction might use magic or some out - of - the - box concepts to make such a situation possible, but it's not part of the official TMNT lore.
In this fanfiction, the TMNT might escape by first observing their captors' routines. If the Shredder has minions guarding them, they could wait for a shift change or a moment of inattention. Donatello might be able to hack into any security systems if there are any. Also, they could use their knowledge of the sewers to find a way out. Maybe there's a hidden passage that the Shredder doesn't know about. And of course, their ninja skills would come in handy for sneaking past guards and making a quick getaway.
Sure was! TMNT originated as a comic. The comic introduced the characters and their adventures, which then led to its success in different forms of entertainment. The original comic had a significant impact on the franchise as a whole.