I agree. I think that these big snakes are pretty notorious for being a tad boring and rarely move but even by just adding guppys that are cheap as chips this exhibit could be alot more interesting.
I'd estimate that about 85% of the exhibit is water, and this photo shows the right hand side of the exhibit. I definitely think that the enclosure could benefit from having some fish in it, and the snake is not a very thick anaconda in comparison to others that I've seen.