Hey there (: I understand you're probably done, but I wanna leave a critique. First, I'll say what I like about the image. The soft colors, and the color choices work well with the style you're trying to achieve. This is for a moe contest, anyway, so you do a good job with making that clear in your piece. The gestures and expression are also quite cute, which is good.
Now about the composition. The piece has a LOT of empty space that doesn't add anything to the piece, which can easily be fixed with cropping. Here, I cropped it quickly in paint for you to give you an example:
Do you see how much more focused that is? In the original drawing, my eyes started to wander around the image, and didn't really focus in on the subject. This time, all my focus is on the girl and the cat-cloud-thingy.
The extremely simplistic background really doesn't add anything to the piece, other than establishing that it's really sunny outside and that she's in water. The water looks very Photoshop 5.0, as it seems like it took you 2 minutes to whip up. You didn't do anything to the sky, either, which doesn't make sense because the sky isn't that bright. It's as if you either wanted to do something simplistic and overdid it, or got lazy and decided to whip up a boring background.
Another thing is the character in correlation with the background. The background suggests that it's very sunny outside (I'm guessing, because it's all goddamn white!). However, there is absolutely no shading on the character. This doesn't make sense, as it's a general rule that sunlike causes harsh shades. The veeeery light skin tone really takes away contrast between her and the background, as well. This is really important in the subject of a piece of art. I know you're trying to express the fact that everything is bright and sparkly, but it really washes the character out and makes the piece feel even more empty. You can darken her skin color as a whole if you want, but what you really need to do is add harsher, more defined shading. Why harsher shading? Because that is what happens when you are outside, during a really sunny, clear day. Here are some photo references so you can get an idea of how to shade this. I'll post mostly light people, in case you want to keep the light skin tone, but I'll throw in tan people as well:
^^ small, but the female has really light skin that may be what you're looking for, so you can resize it in a seperate program to get a better look
Another thing about the shading is that you seem to forget that light reflects off objects. Realistically, the blue in the water would reflect onto the character. Animu example, since you can't seem to get enough of animu:
You get the idea. And since you're probably thinking, "but this is manga styled, it's suppose to have simplistic shading like this!". Yes, manga art tends to have simplistic shading, but not so simplistic to wear it ignores shading rules. Take a look through these pictures:
Now onto the lineart. I see what you're trying to do with the lineart, and I respect that, but it doesn't work well at all with the colors and you seem to exaggerate the brightness effect on the lineart too much. The character is already extremely light, and without the lineart, she just gets lost in the extremely bright background you left. This type of brightness would only really make sense if there was a huge ass lamp surrounding her or something. So you should have done normal lineart, or thicker than normal with the parts in front of the background thinner (but not so thin to where it's disappeared).
And now! Proportions. Since this is a stylized piece, I can't nit pick too much. But I will say that the left leg is very awkwardley shaped, almost like it's bent back despite the leg stepping in. Look at how your own leg bends when doing that same pose. Also, with the right leg (the one bent up), the foot looks like it's floating behind an amputated leg or something. You should have drawn the calf area. Also, by the way you shaded the right leg's knee, it suggests that the knee is pointing down. However, that doesn't make sense since the height of the thigh/knee means it's pointing upwards.
Another thing, the left boob is drawn bigger than the right (unless you purposely want her to have asymmetrical boobies), and it's suppose to be a bit higher than the other since the raised arm is moving up the left side of her body including the boob. Also you put the thumb on the wrong side on the right hand.
One last thing and I'll leave this drawing alone. Her bra doesn't make sense at all. It seems like you drew it normally, but then scribbled in a line and decided that means her bra came undone. Realistically, the bra wouldn't stay put like that. It would be be all bent and moving and shit. Here, I doodled an example:
Obviously don't trace it or anything, I'm just showing you what I'm talking about
Now I have this to say. You were doing great with your realism. In fact, it looked 100% better than what you do now, and if you continued, you could have been really beast at art. Switching to such an extremely simple style really seemed to backtrack your progress though, as you seemed to throw away all knowledge of shading, anatomy, etc, just so you can achieve a specific style millions of people do. This is not good for someone who wants to improve in art. I really suggest you try realism again, and get into learning basic anatomy and proportions as a whole. You can still do the anime stuff on the side, but if you're really serious, you need to learn to understand shapes, shading, movement, contrast, etc. If you can't do this, what makes you think you'll be able to improve any further?
PS. okay okay one last thing I noticed, you shouldn't have added lineart to the water splashing up onto her foot. It doesn't make sense since the rest of the water is so simple.