How to remove the water pump?

1995 Oldsmobile Aurora Northstar mileage: 106,000. I am in the process of changing the water pump and came to a halt. I am trying to take the water pump off but it won't come off. There are prongs on the pump that you have to grasp in order to remove the it, but I can't turn the pump. Is there a special tool you need to get the pump off? I just need to unscrew it so I can replace it with a new one.