There are a lot of times in model and miniature scenes when you can use a 'frozen moment' to suggest something has just happened. One of the easiest to make is a splash that shows something has just entered a liquid, or been spilt from a container. The steps used to make this sample splash of milk in a cereal bowl in dollhouse scale can be used to show the splash as a frog or fish jumps in a pond, or as soap hits a bucket, or for spilled drinks. The splashes use very simple materials. Tar Gel Acrylic Medium is my favorite, but you can also use clear drying pva glue. Either of these materials can be colored with watercolor or acrylc paints in small amounts.
For the most realistic splashes you will also need a small smooth metal or plastic cone shape. I used the cap on my glue bottle, but you can use an appropriate sized bead to make smaller or larger splashes. The base of the splash should be the correct size for the size of the object entering the liquid. If you don't have an appropriate cone shape, you can make the splash on a piece of plastic straw, and cut it to shape it for your purpose.
To make the splash in the bowl of cereal shown above, I used a small glass bowl, sized suitable for dollhouse cereal bowl. I made Miniature O Cereal from polymer clay, you can also use air dry clay, and I shaped a strawberry for the splash from red polymer clay rolled on coarse sand paper for texture. I used a tiny amount of white acrylic paint (tube acrylic), and less than half a teaspoon of PVA glue or Tar gel medium for the splash itself.