This is actually probably one of the biggest reasons people will get stung by their pet stingrays. We see them every day as these cute little animals that we have little fear of, but they don't know anything about us, and are generally scared of things they don't know or understand. We have all seen our rays get spooked by something and dart across the tank or hide really quickly. It is that very reaction that will lead to someone getting stung. We know that when we are cleaning or redecorating the tank we aren't going to harm our rays, but they don't know that. Most of the time they will just find an area on the other side of the tank to hide while you are messing around in the tank, but its that slim chance of them wondering over to your area, or you moving over to their hiding spot and spooking them that will cause their reflex to trigger and sting you. They are just scared they don't know.