Q: "Someone dressed in scuba gear has a body of water behind him." Does this mean that "The person is in the water."?
A: no

Q: "Four males playing music in a band." Does this mean that "Two guitarists, a drummer, and a keyboardist play music together in a band."?
A: it is not possible to tell

Q: "A girl blows up a yellow balloon." Does this mean that "The girl took a nap."?
A: no

Q: "A group of riot police standing around." Does this mean that "Riot police standing."?
A:
yes