We are going to make a nice refreshing glass of seawater, complete with aquatic life and a shark.
Some decisions had to be made on which images to use, for the glass and what pieces of ocean we want inside of the glass. So to better decide, I opened all of the images I had and picked a couple.
Starting with our glass.
Draw a selection box around the glass of water using the Polygonal Lasso tool.
Open your first piece of ocean scene and copy it. Go back to your glass of water, and while that area is still selected, paste the ocean into the glass CTRL+SHIFT+V.
Scale it down CTRL+T so it fits better at the bottom of the glass.
Do the same with another ocean picture, perhaps with a shark this time. To reselect the shape you had before that was around the glass, hold CTRL and click on the mask it created in the Layers window.
Be sure your coral picture is on top and that the two images overlap one another. To change the order, drag the layers around in the Layers window.
Use the Eraser and a Soft Round brush and carefully go in and blend the two images together by erasing some of the coral picture.
Merge the two ocean pictures together when you’re finished blending.
Now, lower the Opacity of the ocean layer to about 50% so you can see the edges of the glass through it.
Using the Eraser again, with a smaller Soft Round brush, carefully trim the image down so it fits inside of the glass.
Select the background layer that has the glass on it. Since this is black and white currently, we are going to Colorize it a blue to match the ocean. CTRL+U and check the Colorize box. Adjust the Hue and Saturation to your liking.
Select the ocean layer again. Use the Elliptical Marquee tool and select a large oval shape, matching the edge of the water at the top of the glass.
Copy the selected water, then delete that shape from the ocean. Paste the water piece on a new layer and match it up.
Change the Opacity on the top piece of water to 40%. Change the main ocean scene to 80%.
Duplicate the ocean scene in the Layers window and flip it upside down, so we can put it into the reflection at the bottom of the glass on the surface it’s sitting on.
Use the Eraser and the same Soft Round brush to fade it into the glass reflection, and change it to 30%.
On a new layer over top of all of the existing layers, make a rectangle with the Rectangular Marquee tool (mine has a feathered edge of 10px, it is not necessary).
Select black and white as your palette colors. Change white to the foreground color and select the gradient tool. Choose the Reflected Gradient and fill in the rectangle so everything is going up and down through the shape.
Change the Blending option on the gradient layer to “Soft Light”. This will create a nice shine down the side of the glass.