Kept you waiting huh? 
Well first things first. I do like the approach you’ve took. Somehow the mix of mid speed drums with the peruvian flute does create something that feels akin to something that would play along a Mario game. However it would feel more under water or beach themed than a lake or the more sombre tones of the picture. But I’m not here to judge, since mine also wasn’t much on point in that regard.
Ambiance wise the I find the song starts strong but then misses its mark slightly. That doesn’t mean it hasn’t any ambiance. Personally I think there could be additional elements that would work quite well with what you have so far. One idea would be to use something like a keys instrument as a waving motion in the background that adds extra texture. Something like stratus (by Olafur Arnalds and Spitfire) could go really well here. Additionally, to add some airy texture, I could very much hear a shimmer verb being useful. The effect could be easily done with a normal plate verb, a delay and an octaver.
Execution. 4/5
Vibe/Atmosphere. 4/5
Composition. 4/5
Listenability. 4/5
Correlation to Theme. 3/5*
*This is mostly due to giving more under water/beach vibes than lake or something that would fit the picture.
