Using this tutorial you can create a water drop effect in Photoshop.
Follow the below steps to create a water drop effect.
1. Create a New layer and draw a circle in it. Keep the circle active.
2. Now Go to blending options and change the fill opacity to 0% percent.
3. Apply drop shadow. choose your own settings in the drop shadow option.
4. Now apply the inner glow. Select the color as white color.
5. Now apply bevel and emboss with depth 191.
6 Use brush tool to pour drops where u want in the picture, in which you want to apply water effect.
Check the sample picture with added watermarks. Do the above steps and add water drop effect to your pictures.