Overall very fun and interesting puzzle game.
Level Design
The levels are nicely crafted, there a quite a few of them with interesting puzzles. The player gets hardly stuck thanks to the question marks. Levels with fish and water scrolling are very well done and interesting. However, the fish mechanics don't make a lot of sense from a realistic point of view, which could be fixed by using an alternative sprite for the fish when out of water (for example they could turn to stone).
Mechanics
The different mechanics of the game are clearly explained and fun to use. The controls are intuitive, very responsive, and feel good to use. I would personally add more puzzles for the torch to make the player more acquainted with the mechanic.
Audio
The game features very nice and unsettling ambient music (reminding me of The Binding of Issac) and good sound effects. An audio slider for SFX and music would be an addition I would like.
Art
The art is beautiful with diverse nicely designed tiles. Although the background is the same image in most of the levels it fits nicely. I really liked the effect of the water scrolling. The only negative is that the player and enemies don't have animations.