This part of the game especially is SO MUCH like the movie Song of the Sea! The fleeing sparklie (or is it sulcha ?) even turns into a seal in mid-air ^^
So, the song for the chase scene is call Unagi. Spotify had played it for me many times, so I was familiar with the album art. Yesterday, I saw what I thought was just album art in a WanderBots LP playlist, my first thought was "THAT'S A GAME?!"
The swimming / underwater part reminds me a lot about the game Aquaria, which is also nice if you haven't played that yet. It's a lot more metroidvaniaish because it focuses also on combat but it also has an interesting story, secrets, upgrades and lots of stuff to explore. And it seems it is also right now 80% off on Steam for 2€ too. :) There are also tools for color calibration that you strap onto your monitor and tell you how to configure it (or come with an automatic software doing it for you).