Hi
I'd say it's possible but rare to lose it deliberately like Krocc did, and then put it all back on again in 24 hrs. But he is an example of a genentically gifted individual. Complex CHO has a high infinity for water per carbohydrate molecule: approx. 10:1. So if you severely restrict carbs then water will certainly be lost. Drugs aside, you'd need to then get wolfing down loads of complex CHO to put the water back on again. Some guys who are carb loading specialists: marathon runners, cyclists etc, can put on 10Ibs in weight overnight from CHO loading during the previous day.
Craig