She might survive by making use of her relationships. For instance, if she has some sort of connection with Loki (maybe from past encounters), she could call out to him telepathically (if there's some sort of magic involved). Loki, being the trickster he is, could then come and rescue her. Another way is that Darcy could use her knowledge of science to create a makeshift weapon or a device that would help her escape from Hydra's clutches. She could use the materials available in her cell to build something useful.
In literature, one of the most famous Darcys is Fitzwilliam Darcy from Jane Austen's 'Pride and Prejudice'. He is a complex character, initially seen as proud and haughty, but as the story progresses, we discover his true and noble nature. He falls in love with Elizabeth Bennet, and their relationship is full of misunderstandings and growth.
In a fanfiction, Darcy could be wearing special glasses that allow her to swim underwater for a long time, like some kind of high - tech Avengers gadget. She could be using this ability to spy on an underwater threat. The other Avengers might not be aware at first, and there could be some comical misunderstandings.
Darcy would likely be both fascinated and a bit intimidated. When it comes to someone like Hulk, she might be a bit scared at first but then get really interested in the science behind his transformation. And for Iron Man, she'd be amazed at his high - tech gadgets and might start asking a million questions about how they work.
Darcy could also be a bit annoyed at times. She's a smart and capable woman. So when the Avengers are overly protective, like not allowing her to go to a certain place for her research because it's 'too dangerous', she might try to argue her case. However, deep down she knows they mean well and it's their way of showing they care.
She also adds a different perspective as a scientist. The Avengers are often focused on the combat and heroics side of things. Darcy can remind them of the scientific implications of their actions. Like when they are dealing with a new form of energy, she can explain how it could affect the environment or civilians in the long run.
Often, his character develops through facing new challenges. Suppose there is a new rival for Elizabeth's affections. This forces him to be more assertive in expressing his love and also to show his good qualities more openly. He might also become more understanding of the society around him, not just the high - society he was born into, which helps him bridge the gap with Elizabeth who has a different social standing.