Use this brush to paint brushes over the underwater part. Press [ and ] to change the size of this brush while painting to make the effect more realistic.
Make a new layer and increase the brush's size. Use this brush to paint some bigger bubbles around the fish.
Convert this layer to a Smart Object and go to Filter > Blur > Gaussian Blur and set the radius to 7 px:
Add a mask to this layer and use a soft black brush to reduce the bubbles' visibility.
Open the window image and use the Polygonal Lasso Tool to select the window only. Place this window onto the middle of the leaves and use Ctrl+T to refine the form of the window a bit.
Add a mask to this layer and change the brushes to the leaves ones. On this layer mask, select one from the brush set (I've chosen Mulberry 1) and hit F5 to change the settings of this brush.
Use this brush to hide the window edges into the leaves.
Make a Hue/Saturation adjustment layer to change the color of the window a bit.
Create a Curves adjustment layer to brighten the middle of the window. On this layer mask, paint on the edges to keep its shadow and contrast.
Make another Curves adjustment layer to increase the contrast and shadow for the window's edges. Paint on the middle to reveal the lightness.
Open the chimney image and use the Polygonal Lasso Tool to select the chimney only to add to the right of the leaves. Use Ctrl+T to make it thinner.
Add a mask to this layer and use a hard black brush to hide the bottom of the chimney into the leaves.
Create a Color Balance adjustment layer and alter the Midtones values:
Add a Curves adjustment layer to brighten the middle of the chimney. On this layer mask, paint on the rest to keep its shadow.
Open the smoke image and use the Lasso Tool to select the smoke part to add to the top of the chimney. Change this layer mode to Screen 100% .
Make a Levels adjustment layer to remove the hard edges.
Add a Hue/Saturation adjustment layer and change the Cyans and Blues settings to remove completely the blue cast of the smoke's edges.
Isolate the birds and add them to the top left of the sky.
Create a Curves adjustment layer to make some dreamy effect for the birds, making them integrated better with the sky.
Make a new layer on top of the layers and use a soft brush with the color #c7b792 with the opacity about 50% to paint around the sea's surface. Change this layer mode to Overlay 100% and add a mask to this layer. Use a soft black brush to remove the light effect on both sides of the sea.
Create a new layer on top of the layers and hit G to activate the Gradient Tool. Press D to turn the foreground and background to default colors (black and white). Choose Radial Gradient and drag a line from the top to the bottom of the canvas. Change this layer mode to Soft Light 100% and add a mask to this layer. Use a soft black brush to erase the effect on the sky and both sides of the underwater part.