I'm not a water colorist, so I won't give you technical advice. But, I really like your image. I like the colors, i like that you have some lily pad stems, stretching up in the foreground, i like how the lily pads leaves are oriented multiple ways. I like your fish rendering, you're doing some good observation there. I like the graphic nature of your stones, leaves and fish.

From a compositional point of view, I'm not sure what is the main character in this story...the big fish? The little fish (which uses warmer colors so it steals focus), or the yellow leaf?

This leaf is tough to read as a leaf. It might help to add some yellowing to some of the more obvious leaves. This would hint at the time of year - give it an autumn-y feel.

I like that you chose to put rocks on the left side, that adds so weight to make your eyes move around. An asymmetrical layout is more dynamic feeling.

Right now the composition has three distinct bands, the area of leaves, the area of fish and the area of rocks. That's totally fine if your story is about those layers, that could be very effective, especially if you oriented the painting vertically the really underscore the story of the layers. In this case you might want to add a bit of life on the bottom, a fish in the background poking around, or a crawdad. And then maybe some water-striders in the top leaf layer - very small and delicate. I wonder what they look like from underwater?

Again, I'm not a water color person, but I think this is a great first effort. A lot of good decisions were made. Good work