Done! Going for 100% didn't take long, after you have all the forms it's quick to find everything so I went for it. I did beat it before completing it but even then there wasn't a lot I hadn't done already.
I liked the game. Great scenery, awesome soundtrack, interesting bosses and some good world design.
My only gripe was with the mid-game traversal. The overall map could get obtuse when it came to figuring out where to go next by yourself, and more than once I'd swim for a long time to some area where at some point I couldn't advance further and then have to go all the way back. This obviously isn't unheard of in metroidvanias but the problem here is that many sections are boring to traverse and sometimes too long for their own good.
At the start it's rewarding, you're reaching all these new vistas and such, but after a while in this type of game, usually by the midpoint, you just want to get to places and be able to return fast through the segments that you already cleared. It's bothersome when you swim for a while, reach an area just to find out you can't advance because you don't have the needed form, then have to swim all the way back because there aren't shortcuts and no feasible way of quick travel introduced to help the pacing (aside from the few and far between Ancient Turtles that you may miss with a wrong turn while exploring).
Yeah, there are ways to swim slightly faster with the fish form etc, but most of the time it's just boring to swim around. It doesn't help that fighting grunts isn't very interesting either. Aside from the bosses and a few enemies it's not compelling to fight most of the wildlife. After you know which ones drop useful ingredients, there's not much of point in engaging either as enemies are easily avoidable and mostly not fun to kill, as you'll just shoot energy shots for a few seconds before you're back on your way. I love exploration in gaming and losing myself going to areas that won't advance the plot immediately, but I feel like the middle section of Aquaria fails in making it gratifying to do so, with too many roadblocks and a conspicuous lack of shortcuts. The bulbs you can open with the nature form would have been good in mitigating this but they are heavily underused and none of them work as timesavers.
This all may sound harsher than I intend it to be but there was a point where I found the moving around to be a chore. Besides that, the game is very well-crafted and offers a lot of content. There's a lot of care put into it and I can see why it was such a popular indie game at the time.