This was the scene on the M74 heading north. If a layer of water gets between the rubber and the road, brakes will stop the wheels rotating but the water will act as lubricant and allow the rubber to slide along. This lack of friction is called aquaplaning. On a molecular level it will be to do with the fact that water molecules have only weak bonds between them so are subject top shear forces, tearing forces that allow layers to slide over one another. good radial tyres allow water to flow out through the valleys in the tread. You can see on the road surface where tyres have dispersed the water leaving clear tracks.
