Very nicely done! You absolutely nailed that Zelda feel, it looks really great. The turn in order was not super complicated but you also didn't just swim around in a circle. The islands were just far enough apart that you could drown on the way there (and I sure did) if you missed or ran into something. I really liked the success sound effect. I liked how the docks led you from one island to the next, it gave me a sense of direction without needing a map.
The first time I played I was a big dumb dummy and didn't realize that the egg lady was putting out the basket for me to pick up, so I wound up swimming to every island and getting all 9 aquastones without making a single other trade, thinking that something would be on another island or was behind a tree or something. And the yellow bananas on one tree being different from the others made me think I could pick it up and give it to the monkey. Again, very dumb of me, but that is what happened.
Really great job on this game altogether! Seriously smooth and polished.