This classic image is strewn across the stock community but seems to be a very popular image of choice for designers.
If you fancy having a go at creating an image like this but don't have the professional set-up or equipment to capture the image with camera then you should try this very simple yet very effective tutorial for photoshop to create the desired effect.
Water drop effect tutorial for photoshop
Remember to make the image bigger than the tutorial states though so you have the desired size that Dreamstime require for submission.
I also found that it helped to reduce the height by squashing it down to give a better effect.
Here's some great examples of great water drop sellers on dreamstime.
Have fun creating and let us all see what you create.