Theme: doesn't really feel like discovery to me. As Merly23 stated, you just follow the arrow.
Fun: this could be really fun, but as it is it feels kind of monotonous. The traveling on the sea feels pointless since you're just following the arrow for what feels like too long, and the mazes are really easy (and all feel the same). With better level design and maybe some additional mechanics (for example, maybe the sea travel is more than just following an arrow across an empty sea to reach the next island), this could be great!
Controls: worked well. Nothing else to say.
Graphics: great! Everything was good quality and well-polished, and separate pieces (e.g., tiles) connected seamlessly so the world felt cohesive.
Audio: love the SFX! I really like that you added the sound of the rustling bushes; that's a nice touch. And the sound for picking up an artifact is nice too. The music sounds good at first, but can get a bit repetitive and irritating after playing long enough. Perhaps make the melody a little more interesting and the loop a little longer.
Originality: mazes aren't original, grabbing artifacts isn't original, seafaring isn't original, but when you combine these elements together you get something that's at least a little original since these things aren't usually combined.