Wow! The art, the music, and the use of light in this game is incredible! Of the games I've played so far from this jam, I think this game has the best atmosphere. You did an incredible job setting the mood.
I only have two minor complaints: 1) the controls were a little unorthodox and I found them hard to get used to, and 2) I had trouble figuring out how to exit the cave after finding all my ducklings -- I kept swimming around looking for an actual exit to the cave.
But really, those are non-issues. This is a great little game, and honestly I think it's a special one. You did a great job!