I don't really know after all, okay for me is not a state of something. It is not positive nor negative unless you add the tone of your voice to it. You need to factor in as well, how your listener will take it. We are so used to getting okay as a good reply when in fact there will always be more to it.
Take the photo above as a sample, one of them can be asking if the other is okay. The simple answer will be "yes, I'm okay." The question should be "How are you holding up?" or "Do you think we can find something here we can use to stay afloat?" This might be overthinking for other but this is a better question than the one on the title. There is more concern on those question.
What if there are really close to somewhere safe, "Are you okay?" is fine as long as there is a follow up like "can you still swim towards the shore or boat?"
Whatever the situation don't settle for an "I'm okay!" or "We're okay." reply.