Start with an RGB image (blank or an image)

Select New Channel from the Channels palette command menu

Invert (cmd-I)

Filter>Noise>Add Noise: 500, Uniform, Monochromatic

Filter>Blur>Guassian Blur: 5

Image>Map>Threshold (Cmd-T) 152

This gives you the base for the drops

Filter>Blur>Guassian Blur: 5
(Cmd-F)

Image>Map>Threshold (Cmd-T) 225

This makes the drops more round and blobby

Filter>Blur>Guassian Blur: 1

Soften the edges a bit

***Oops! The following line is corrected***
Select Duplicate Channel from the Channels palette command menu

Filter>Blur>Guassian Blur: 5

Select>Load Selection> #4

Delete (delete key)

Deselect (cmd-D)
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RGB channels (cmd-0)

Select New Layer from the Layers palette command menu

Press the X key to swap colors

Select All (cmd-A)

Press Option-Delete to fill the layer w/ white

Filter>Render>Lighting Effects:
Light Type: Directional, Intensity 25
Properties: Gloss 100, Material -100,
Exposure 1, Ambience 0
Texture Channel: #4 copy
Height:15, leave White is high unchecked

Select>Load Selection> #4
Delete
Deselect (cmd-D)

Set layer mode to Multiply
This sets the shadow for the drops

Select Duplicate Layer from the Layers palette command menu

Image>Adjust>Levels
Set the first input level to 230

Set the layer mode to Screen
This sets the shiny highlight for the drops
To see more of the image, set the opactiy to 80%

You now have water dops splashed over the background layer. Put what you want the drops to be over on this layer. Fill it with a color or paste in a picture.