Hi, I've been playing Guild Wars 2 for about 5 years now and I would like to give you some ideas that you could have for Guild Wars 2 as either a mastery skill or an expansion. One is that it would have been fun if you could create a playable mermaid race/breed that you could have in an underwater world. Or that you could have the mermaid in a mastery skill and that then your character could get a fin/tail as soon as you go underwater and that you could then swim, throughout Tyria.
The second is that you could have an underwater mount that you could ride on and fight against other animals, like in the story, under the sea/ocean. In that case, it would be a new mount and not a mount that already existed, such as the skimmer that already exists. It could be a mount such as a seahorse or another mount. With the hope that you got a couple of ideas that could be implemented in an otherwise amazing game.