MarkoH01: Relaxing? I have Aquaria installed since years and still have not finished it because of some pretty hard regions and because of it being so big (keep in mind that I am used to playing 8-10 hour long point and clicks) :)
Yes, the world really is pretty huge. I remember being really glad for the ability to put your own notes on the map as reminders for things to explore / solve later.
I call it relaxing because there's (almost) never any time pressure (I can think of only one real exception), most things which can hurt you are easy to avoid or deal with once you gain the appropriate forms (and excepting the dark area), there's effectively no annoying tricky jumping puzzles (except if you really want to finish every single secret beyond the veil), and so on.
I do admit I might be remembering only the good bits and seeing it all through aqua colored glasses, as it really has been very many years since I played it completely. :)