This is not something you can with Adobe Photoshop in one minute, but it's pretty fast and the result is so close to reality that you won't see anything unusual. It's all about combining the right filters in the right order and of course, it's easy to achieve this effect. On larger images looks even better, but for the sake of this tutorial I used a rather small image to fit in the pages of the website. So, let's see how Photoshop can help us...
First you need to open an image with water. This can be an image from the beach, a pond, a pool or anything where you can have a person standing in water.
Now we will think ahead a little. Duplicate this layer, drop the color information (Ctrl + Shift + U) and save it as map.psd. We will need it later. After you saved the file, you can delete this new layer.
Next thing you do is to bring into this image, into a new layer, the person that will use. You can use objects too, but make sure they are isolated (that means without any background).
Now we need to tweek a little this layer, cause when you stand in water, your feet don't look like a straight line where they go into the water, so we need to adjust that with the rubber tool. Just round the edges of the feet where they meet the water.
Unless you are a statue and the water is still, you're going to have some ripples around your feet while standing in water, so we're going to do that now. Behind our current layer, create a new one and fill it with 50% Gray (Shift + Backspace).
Now render some clouds. Remember that you need to have the default colors set for foreground and background. If you don't have the default colors of black and white, just hit D key before rendering the clouds.
To achieve that ripple effect we need to apply 2 filters. Go to Filters - Distort - Twirl and apply it. Those numbers work for my image, but you may wanna try different values, according to your image size.
After this effect, go to Filters - Distort - ZigZag and apply it. Again, you may wanna change the values to work better with your image.
After that, use the transform tool (Ctrl + T) to adjust the size of this layer and perspective to make it look real. Position it so one leg of our person fit in the middle of this ripple, add a layer mask and hide the margins of this layer so it looks round and set the blending mode to Soft Light. This is how your layer should look:
Duplicate this layer (Ctrl + J) and move it to the other leg. Now your composition should look more or less like this:
Now for the actual reflection in the water, duplicate the layer on top (the one with our person), flip it vertical and position it where it should be. Drag the new layer below those 2 layers with the ripples and set the layer transparency to 30%.
Remember where we started doing this, we saved a map.psd file? Now we're gonna make use of it. Select the layer with the reflection and go to Filters - Distort - Displace. Again the values may change for you.
After you hit OK in this screen, Photoshop is going to ask you to chose a displacement map. Guess what? Chose that file you saved earlier.
Now do the same thing for the 2 ripple layers. If everything worked fine, this is how the layers should look like for you:
... and this is how the final image should look like:
Pretty close to reality, don't you think?