It's not a dumb question. They don't really jump out but they can lift themselves over the side of the tank. The waterlevel in my tank is only 5 cm from the top so I make sure my tank is closed, especially at the sides.
my ray tank is next to my bed and I am constantly woken up by my rays spitting water at me......, they get their mouths completely up and over the side of the tank and spit at me.....