Welcome to the Dio section Martin.
As Scott mentioned there's a fair bit of useful references in the Kitmaker as well as the Feature section. There was a build log by a fellow modeller on simulating very realistic splashes a while back but being an old guy poor memory I can only recall the scene of someone jumping into the water from a float plane.
At any rate, some if not most water making products have a tendency to self level making creation of splashes difficult. So far I've used 2 products, one being an acrylic glue used to seal glass, acquariums, etc and the other Envirotex Lite. The first is a glue from GE as in General Electric. You can get a glimpse of the glue in Photo #15.
https://hfmodeling.kitmaker.net//features/1207&page=6 About 20-30 minutes or so you can tease the glue when it starts to harden with a toothpick to make splashes provided their not to high. Otherwise add the glue to your existing splash to get some height. This glue will not self level and you can even tint it with acrylic paints such as white to simulate splash. A splash is essentially a disturbance to the water surface which depending on the size of the splash is accompanied by foam. Foam to the human eyeball appears white although water is essentially transparent, well clean, clear water anyway. So adding a tinge of white mixed with the material you plan to use to make the splash around the area of the tyres will help further the illusion of a splash.
Envirotex is generally self levelling but around the time it starts to harden which is about 15-30 minutes time depending on the air temperature you can actually tease it a bit just like the acrylic glue above.
Here's a dio I did a while back using a combo of Envirotex Lite as the base with a little bit of GE Acrylic glue to top it off to simulate splashes against a rock and a semi-submerged branch in a river.
Hope it helps.
white in the bottle but dries clear will do. Get a few cotton balls, 
and pick out some strands. Attach them where you want to show white splashes.
