Sharing my pic as my 2 cents worth.
Click for larger image.
When you mention JOY - first thing comes to mind is facial features - a smile, or the sparkle in the eyes. Other joyful reactions can be the moving hands, its not static. What I see in your pic, may have that element of joy, but with such posture, it lacks punch, but more like wanna approach me with a punch - see his right clenched wrist. What could have done was him screaming, or smiling with the hands in the air - OR instead have the water curtain pouring on his head from the back trickling down his smiley face. what we see now is lots of water splashes / droplets which mess up the picture. My suggestions MIGHT produce a better pose and shot; and with the usage of flash to freeze the moment, you COULD have captured it better.