That wasn't the case. Billy only wasn't worried because he didn't have to get hit. Besides, seeing their projectiles should be easy as long as he can see the enemies. If the worst comes to the worst, he can always dodge if he fails at blocking the attacks with his spear. Regardless, once he grabbed his weapon with both hands and then approached the river. Using Block Mastery should be possible without damaging the weapon. It was only spheres of water, after all.