I'm always telling clients to carry water whenever they workout - hydration is key. And I'm not the only PT saying it either. This from a fellow PT in UK, who is currently training for a marathon. "There's a direct correlation between body hydration and body fat. Your body fat comes down when your hydration goes up but it's harder to digest food and flush out the toxins if you are dehydrated. I don't drink water when I run unless it's for 60 mins or more, so those sub hour runs leave me pretty dehydrated and not listening to my own advice!"
The great thing about bootcamp/circuit training is that your water bottle is right there nice and convenient and you can have it whenever you want to. It's not lazy or cheating to help yourself to water. Every single cell in your body needs water and functions better with it.