Tidus is aware of the action taking place--he doesn't want anything to happen the guy, charging in recklessly or not (hey, who doesn't now and then, right?). But he sees the fire too, and Danny doesn't need to be warned for that--

Instead, he may hear a sizzling and a hot smoke as fire and water collides behind his back, but without smacking him in force. "Keep going!" Tidus calls at him, and he'll do what he can to keep conjuring quick and small water balls to aim at the raising fire.