Liquid metal provides a great modern-looking result, but you can also colourise the image for a quick water-looking effect.
Make a new image with a white background.
Press D on your keyboard, then go to Filter > Render > Difference Clouds.
Press Ctrl and hold down whilst you press F. Next, go to Filter > Sketch > Chrome and make Detail 8 and Smoothness 6.
Go to Image > Adjustments > Brightness/Contrast. Set the Brightness to 15 and the Contrast to 50 and press Ok.
Finally, go to Image > Adjust > Auto Levels and you should end up with something like this: