Why does the rescuing naval officer comment,"I should have thought that a pack of British boys would have put on a better show than that?"
Go into detailed descriptions of acts of uncivilized degradation and supreme cruelty committed by the impulsive kids.
The naval officer's comment is revealing the shock he feels at seeing the boys uncivilized manner and attire. He expected that proper British schoolboys would carry on in an appropriate manner.
The savagery that had proceeded this rescue is evident to the boys. They have evolved into a roving band of hunters/killers who have given in to the constant demand for blood-lust.
At first, just hunting the boars for meat was enough, but as time went on, they found each other was more exciting game.