Not really.
You do dehydrate but if done correctly it's no problem.
Night before the show I would drink a bottle of dry white wine (see- not so bad) and then not drink any liquids until after the show (maybe 18 hours later).
In the mean time I would cram in carbohydrates from complex through to simple sugars just before contest time. The sugar keeps you going and you don't really notice the lack of water.
There are more risky techniques using diuretic drugs which can often leave the user pretty shaky come competition time. On those you do have to consume water and it's a delicate balance - easy to get wrong.

I actually liked the off season a lot more - being big and strong and allowed to eat pretty much anything .