Who knew that rain was in BeamNG all this time?!
NEW IN UPDATE 2.4:
Texture Improvements
Sometimes there are floods in the immediate vicinity of the beach. It must be one of those floods. It is not as flooded as it used to be; therefore, the road is wet even in tunnels.

I know the roads aren't super shiny. This is 50% due to laziness and 50% to make it more potato friendly.