A typical olympic pool (assumed 50m x 25m x 2m; the depth actually isn't standarized), contains 2500m^3 of water. 1m^3 of water has a mass of 1t (in typical conditions).

So 10^6 tons of water corresponds to 400 olympic swimming pools. That's quite a lot of water (still not much compared to the volume of the oceans, of course).

You're right, I was going off the parent. They made an error somewhere, 1 million tons is 240 million gallons, not 2.4 millions.