Definitely the waterpump! It will only overheat again, and in very short order.
Let's hope it didn't do major damage!
If the waterpump impeller is shattered, like many are, there could be pieces of it throughout the cooling system. If there are any pieces unaccounted for, you will have to backflush the cooling system.
It's likely that after a new waterpump, all will be ok.
-Lance
