The first puzzle that requires the waterbolt requires you to aim at a projectile switch off-screen, and bounce the bolt between that one, and another on the same block height far off. I found this to be in poor design. The concept itself is fine, but having no visual cue as to where you should be aiming made that puzzle far more luck-based than necessary. It was rather difficult to actually aim at the right spot to do this, especially since the target was off-screen. Having to blindly aim at something with nothing to go on made it frustrating. Some sort of visual cue to help understand where you should be aiming would help a lot, and reduce the annoyance of that puzzle by quite a bit. Something like a torch maybe halfway between the 2 projectile switches, or perhaps a torch on each side near the projectile switches would be nice.
For clarification on which puzzle this is, it's the one where you need to get a waterbolt to bounce between 2 projectile switches, which toggle a series of five walls between actuated and not. Every other wall is actuated by default, allowing you to only pass through one wall each time the waterbolt hits one of the projectile switches. It is in... I believe the fourth level. It is the level that is on the top area from the level selection area.