The medium-sized hole leaks at a rate of one-half that of the largest hole, or 3/2=<<3/2=1.5>>1.5 ounces per minute.
The small-sized hole leaks at a rate of one-third that of the medium-sized hole, or 1.5/3=<<1.5/3=0.5>>0.5 ounces per minute.
Combined, the three holes leak at a rate of 3+1.5+0.5=<<3+1.5+0.5=5>>5 ounces per minute.
Since one hour is 60 minutes, two hours is 2*60=<<2*60=120>>120 minutes.
In total, over the two hours, the three holes will leak a combined 120*5=<<120*5=600>>600 ounces of water.
#### 600