The Pokemon at the camp turned out to be hostile. Josh and Matt rushed ahead to join Anthony when they saw him get attacked. This guy was obviously very powerful, and to make matters worse, the tunnel behind them collapsed, blocking their only exit.
"Sorry, I forgot to give this to you before." Matt said, pulling Anthony's helmet put of his bag. "I grabbed it when we went looking for you earlier." He then turned towards their opponent. "I can't do anything to damage him, I'm afraid." He began putting up Light Screen and Reflect, since that was really all he could do.
"I can." Josh said. He used Water Gun, but didn't do that much damage to him. No surprise there. What did surprise him, though, was how much energy it took to use that attack. He could normally fire multiple Water Guns in a row without any trouble at all. Why would it be so difficult this time?
He decided to ignore it, and assumed that it was just his imagination. Fighting the Tyranitar was their top priority right now. He couldn't waste time worrying about it.