Balian is ideal Bull Shark Habitat and reports of bites have been reported there for well over 30 years, its just we don't here about tit over here.
Other paces where the river meets the sea with the estaurine quality salt/fresh water mix is usually rife with Bull sharks and there's quite a few in Indo but Balian has more visitation than the other spots so the recording of the events is better captured so its better known for it accordingly. There's been accounts of Bull Shark bites in Sulawesi, Java, Lombok also,as well as Green Balls that im aware of. Green Balls about 20 years ago there were 3 bites in two weeks apparently (could be a myth?)
All That aside though, i love Balian, great wave, not worried about Bullsharks as much as i worry about the potential of picking up Hep-A. If you were what goes into that river a little further up the catchment ....eeeewwww