UNDERTOW To find the perfect Southern rebel for David Gordon Green's film Undertow (coming in 2004), producers went deep into the heart of...England? That's right, y'all, British-born dancing king Jamie Bell (Billy Elliot) has gone Dixie. Currently shooting in Savannah, Ga., with Dermot Mulroney and Josh Lucas, the 17-year-old plays a troubled teen on the run from his maniacal uncle (Lucas). ''It's dramatic, adventurous, romantic, and touching,'' says Bell. ''And on top of all that, you get to see me pull off a convincing American accent...or at least I hope it's convincing.''