Hi! I am a HUGE Captain Swan fan! What are the main reasons why you love Captain Swan/Hook?
Well, I fell in love with Captain Swan at first sight to be honest with you. When the group discovered Hook under that pile of bodies and Emma and Killian looked at each other, I just felt the chemistry straight away. And as we saw more of them, each of their interactions made me ship them a little bit more. I love how similar they are on some points (kindred spirits alert!), I love how they healed each other, I love how they made each other grow and how they always fought for each other. I love that Killian tore down Emma's walls, which allowed her to truly love again and how Emma helped him find his way back to the good man he was deep down. I love everything about them, really! And to this day, they're still my OTP even though I'm a quite big shipper and I have tons of other ships.
And about Killian more specifically, I love that he is a complex character with lots of layers and that, even though he doesn't always make the right choices, he always ends up owning his mistakes and trying to set things right because he's a man of honour. I love his sass and his innuendos but also his more gentle, caring and loving side. I love his development throughout the show and I think he had the best redemption arc of all! And let's be honest, I also totally fell for his good looks :p
So here you go, anon! These are the main reasons, I guess, or at least those that come to me from the top of my head. But the truth is, I could probably dissert about that subject for hours if I gave it more time and thoughts xD (For example, there is also a lot to be said about how these two characters ended up being so lovable and having so much chemistry because they were played by amazing actors such as Jen and Colin!) Anyway, thank you very much for your question! :)