For this first stage, I advise you to carefully observe an image of a splash in order to draw the base of the form. It is necessary to start by painting with a soft, small brush (opacity set to stylus pressure), in white, the initial form of the splash. If you observe an image well, the contour of your form shouldn’t be well-defined, but rather painted with small, successive touches where the opacity varies. This, I think, is the most delicate part to make.
On a new layer, placed under the old one, paint the interior of the form with a neutral gray. With the burn and dodge tools, add highlights and shadows.
Change the layer to overlay so that only the density effects are shown.
To create little splashes which accompany the big splash, you have to create your own type of brush. For this, create a new document and with a soft brush and black color, paint a shape like the one shown. Then go to edit > define brush preset.
To correctly use this shape, it will be necessary to configure some options in “Shape”. Follow the screenshot provided.
Now, paint this shape in your document. It is necessary that these droplets look separate from your main splash. In short, try to paint them mainly around the edges of the splash.
With a very small brush, delicately paint the interior of the splash. Do it on a new layer, whose opacity you can adjust so that the splash is only lightly textured.
If you want a more pronounced effect, merge the layers of the splash and duplicate that group. Then put that copy on Soft Light. This step is optional.
On a new layer, with a soft, white brush, add some details and bring out some brighter areas.