Horses sometimes paw at water to test the ground underneath to get an idea about the depth of the water. You may notice your horse pawing at the water. While pawing may give you the impression that your horse is having fun, he might be doing it to roll after finding the ground. Hence, it is important that you stop him from pawing immediately to let him know that you have control over him. Or chances are that he would roll suddenly - which can lead you crushing under his weight - and that would, be detrimental.