Yeah, I know what you mean how safe showers can be given. Monty sometimes looks dehydrated (he now drinks just fine) so I bring him in and gently shower him with warm water, bouncing off the wall like people say to do.
Perhaps they got a big water drop into the chameleon's airways? I remember once I squirted a tiny bit of water into Monty's mouth and then he was "sneezing" for around a couple seconds, then stopped. Maybe I got some in his airway. I found out you're not really supposed to squirt lots of water into their mouth unless they lap it up or something.
Maybe it swallowed some the wrong way.