Okay, my water is done.
Oh no, Ive made my sky too purple blue.
1. Select the sky layer
2. Apply a hue correction - take a color you like.
Here I reduced the 'blue-ishness'
Your choice really. Select a different color here if you want.
All the hard work of masking is done. Play with colors if you want.
Think it still looks fake ? Well, change it