In my limited experience with monitors, I have found water monitors to be mostly unpredictable and actually downright nasty. Here's one creature that will hurt you a lot more than any ratsnake because when they bite, they will not let go.
I've been fortunate to get a WC 1.5ft juvenile water which has so far been well behaved enough not to try and bite or lash at me. However, this tends to be the exception than the rule as, more often than not, they will be on threat display even as you open the cage door.
So far, savannahs seem to be a lot more docile than waters and I've had no problems handling them. Again, I must stress here that my experience with them is limited and have only come across tegus (also very nasty), savannahs and bengals besides waters. Of course, only the water and bengal are native to my country.
In the main, while it is possible to have a calm and tractable monitor, one must never forget their potential for damage. Good luck and take care.