Open the image you want to use - here, I've used an image converted into black and white, but you can leave your images in colour, convert them to black and white or use an image toned with any colour you choose. The base image you use can be in any style you like - you'll just need to be sure the image you use to overlay the base image is a good blend in terms of colour.
I found a photo of water splashing up behind a boat (in fact, I took a bunch just to use for this - later this week most of these will be available on Free-3D-Textures.com in the Stock photo & water textures sections if you need some to use).Next, I cropped out the parts of the water splash that I wanted to use. Then copied that to a new layer on top of the photo. To do that, with the water image active, choose "select", then "all" from the menu in photoshop. Then, select "edit" and "copy" from the menu. Minimize the water image and make the people photo the active one. Now, select "edit" and "paste" from the menu to paste the water image onto the background (people) photo.
Depending on which method you selected as the layer blending mode, you'll get different results. The method you select will depend on the background photo you've chosen.
The blending method for this photo was "multipy". You'll notice there is still some blue showing in mine - that's because I decided not convert the water photo to black and white, but you can convert it and get different results.
To get this smoother, ink-stained effect with texture, the water splash (layer 1) layer is set to multiply. A second watersplash layer is added on top of it (layer 2) and then: select edit, transform, flip horizontal, blending mode overlay, with advanced blending styles. The advanced layer styles should have a deep knockout and adjust the amount until you get a look you like. To add the texture, select the layer styles palette (double click on the blue part of the layer label to open the layer styles, select the texture option and choose a texture pattern to cover the photo with. When happy with the result, flatten the layer and adjust the curves.
To get this "damaged photo from a slide" look, I converted the watersplash photo to brown and used the layer blending mode "color burn".











