"You have to know them but you have to go with the flow of a game for yourself"

Why do referees whistle different in many countries? Is this the case and when yes what do we have to do? Everybody acts on one set of rules and therefore there are no differences regardless of the country. As a referee you don't have to look angry to players or coaches during a game. But at the end we need to establish another level for referees (and players and coaches maybe also) that is more professional. It's not acceptable that we have only pure amateurs within the waterpolo scene.