8/10 - The way the colors have been artificially darkened is a little distracting, but otherwise, I really like it. The placement of Blastoise on the background feels so natural, it really looks like it's walking on the ocean floor. Those three bubbles in front are a good focal point, too.
The character is simple, but well-drawn. The lighting and direction of the wind are consistent. The background could likely be replaced with transparency, but I'm not one to talk; my avatars are the epitome of useless backgrounds. However, the drawing features colors very similar to that of the background, so I would recommend changing the color slightly.