GoPro's surf kit comes with a leash that attaches to the camera to the board. If you don't have that kit, just attach some braided fishing line or something to it. The leash point on the camera is at the center of the steel pin that hinges the housing's door, you'll see the location if you look.
My Conotour HD waterproof case let's you turn the power on and off on the back and there is a slider on the top to start and stop recording. All purchased in 2011. So, I'm not sure why you thought you had to remove the camera from the waterproof case.