Hey Nate, this is so peaceful and enjoyable to play, I really am having a good time with it. I love the water shader you're using, especially with the little pink neon edge on it that adds a little bit more visual stimuli. I also love how it feels to skip the rock, the bounce on the water is exactly what I want when I press space and it goes back up in the way I expect as a player.
In terms of critique, I think I would spend a bit more time modeling the rock, or adding something into the game to pass by the rock as it goes forward, in order to continue to keep the player's attention while they're playing. I don't think such a thing would even have to impact score, maybe just a buoy or a seagull or something.