Really nice work @malcom! Hope it's ok I did a quick paint over as well, got a couple of notes for yah.
First: The composition you have is great if you like you can make it a bit more dynamic by taking advantage of the nice diagonals you had set up. I kind of just gave the character and her glowy friend a nudge towards the areas of interest. Also seemed like a cool idea to tilt the fish in the background to line up with the rest of the composition.
Second: Think the value range of the glowy eel needs to be closer to the character since they are close together, and the eel is emitting light. My thought was to bring some of the lighter values you have near the hands over to the head of the eel. The forms and wrinkles on the eel are super successful. What's your method for painting glowy semi-transparent stuff?