Adding more non-homing projectiles sounds like the best idea to me... And I'm really not sure how that could possibly make it easier. Make it so, for example, before the mouth starts opening to fire the beam he shoots out a wave of projectiles from all parts of his body, but at slightly different times so there are gaps. Then Naija has to swim between them as best she can and get into position to hit the head in the mouth before it fires.