In that case WillStill, we agree.
I thought you were saying just provide a water dish.
Of course, providing them with a pool big enough to actually swim would be out of the question for most hobbyists, and not "needed".
Just somewhere big enough for the animal to fully submerge, and 30 to 50gals would be adequate for most (another matchbox sized offering)... They`re so accomodating, these varanids!